Jantar Mantar ("calculation instrument") is an outdoor complex of large-scale astronomical instruments located in New Delhi. It was built as an observatory in 1724 by Maharaja Sawai Jai Singh II (r. 1700-1743) of Amber, a Hindu Rajput king, at the request of Muhammad Shah, the reigning Mughal emperor at the time. The complex was originally located in a vast treeless landscape south of the medieval walled city of Shahjahanabad, in an area called Jaisinghpura, which was also a part of Jai Singh's estate. Jai Singh remained a supporter of the Mughal hegemony despite their waning power at the time of his rule. As a gesture of appreciation, he was made the governor of Agra and Malwa by the emperor Muhammad Shah (reg.1791-1848). The construction of the observatory, the first of its kind, by a Rajput king near the Mughal seat of power and at the behest of a Mughal emperor was indicative of the political goodwill that existed between Jai Singh and the Mughals.
By the end of the eighteenth century, the condition of the instruments had deteriorated severely due to general neglect and vandalism. The then-Maharaja of Jaipur initiated a restoration in 1852 which was completed by the British in 1916. During the later stages of restoration, a Mughal garden was laid out around the instruments and a boundary wall was built to protect the site. In the nineteenth century, when the British planned their colonial capital city of New Delhi to the south of the walled city, Jantar Mantar came to be located in the midst of the commercial district, Connaught Place. Today, several post-independence commercial and institutional buildings surround the Jantar Mantar complex, now located in the heart of the city. While the complex is presently used as a public garden (2009), a ticket is required for entry. Within the boundary wall, all the instruments are accessible to the public, giving the complex the appearance of a playground for adults and children alike.
Jai Singh, enamored of architecture and astronomy, is believed to have designed several of the instruments in the complex himself. He followed the Delhi Jantar Mantar project with a more elaborate one in Jaipur, subsequently commissioning three other observatories in the cities of Ujjain, Benares and Muttra. The ones at Ujjain and Benares have also survived. He felt that the brass instruments used at the time were limiting due to their construction, smaller size and number of calibrations. The instruments in the Jantar Mantar complex and his other observatories were designed to facilitate precise observation and recording of measurements related to the celestial bodies; each instrument is built anthropometrically, with staircases and openings for easy access.
At present, the complex comprises of four large-scale astronomical instruments: the Samrat Yantra ("supreme instrument"), the Misra Yantra ("mixed instrument"), the Jai Prakash Yantra ("victorious light instrument") and the Ram Yantra ("Rama's instrument"), located within an outdoor manicured garden, approximately 230 meters north-south by ca. 100 meters east-west. The site is accessed axially from the north. From the entrance, the Samrat Yantra dominates the view, as it is located on the central axis of the site. Walking through the complex from north towards the south, the Misra Yantra is encountered first, along the western side, followed by the Samrat Yantra in the centre of the site, flanked by the hollow hemispheres of the Jai Prakash Yantras. The Ram Yantra is located at the southern end.
Samrat Yantra: The Samrat Yantra is the largest instrument in the complex. Geometrically it has two main components, a gnomon and a semicircular surface. The gnomon is essentially an inclined surface or line at the angle of the earth's meridian (the inclination of the earth's axis). The structure of the gnomon comprises two right-angled triangle walls, such that the base of the right triangles is also the base of the wall. A staircase sandwiched in between the walls allows access to the very top. The geographical latitude determines the angle between the hypotenuse of the right triangle and the horizontal surface. The edges of the hypotenuse, on either side of the staircase, are calibrated for measuring the zenith of heavenly bodies. The gnomon is intersected by a semicircle, which is in turn inclined at an angle so that it is parallel to the equator (or perpendicular to the inclination of the gnomon). The semicircle is constructed as two curved quadrants, also not a single dimensioned line but a surface with calibrations; the entire length of the curve can be accessed through staircases running along its surface and on either side of it. The time of the day can be measured from the markings on the curved quadrants, determined by where the shadow of the gnomon falls during the course of the day. The zenith (sun's height in the sky) can be measured by observing which part of the gnomon casts a shadow on the quadrant. The staircases allow the observer to access every significant part of the gnomon and the quadrants to allow the recording of measurements.
In plan the gnomon is oriented north-south, with the lowest point of the hypotenuse towards the south and the apex towards the north. The base of the right-triangle walls of the gnomon stretches for about 35 meters. The highest point of the gnomon is accessed via a steep staircase (1.5 meters wise and rising to ca. 3 stories above ground). The right triangle walls are punctured with openings to view the enormous structure. These openings are spanned with typical Mughal keel arches.
Misra Yantra: The Misra Yantra is located in the northwestern corner of the site. It is a relatively small instrument, and may have been built by Jai Singh's son, Madho Singh (reg. 1751-65) sometime between 1759 and 1799, as the instrument is not mentioned in Jai Singh's accounts. The entire instrument measures about 25 meters across (east-west) and 12 meters north-south.
The Misra Yantra is organized symmetrically about a wall whose upper edge is inclined to the horizontal plane at the same angle as the hypotenuse of the Samrat Yantra. This wall is formed of two walls flanking a staircase used to access the top; while smaller, it is similar to the Samrat Yantra gnomon. The wall is 8 meters high, and and its base stretches for ca. 11 meters. A pair of semicircular scales are located on each side of the gnomon, with their centers located on the hypotenuse of the central wall. These four scales are marble strips, .5 meters wide and supported on individual curved walls. A staircase, about 1 meter long, runs between each pair of scales. The semicircles on the eastern side are inclined at angles corresponding to the meridians of Greenwich and Zurich. Like the hypotenuse, their inclination is upwards from south towards the north. The semicircles on the western side are mirror images of the eastern pair, and correspond to meridians of places in East Asia. This may be coincidental, as the symmetry of the instruments appears to have been the overriding determinant of their inclination. The calibrations on the marble scales can be read by climbing either the staircases located along the outer edge of the curved walls or the staircases in between them. Two doorways, about a meter wide and spanned by segmental arches, puncture the outer curved walls on either side of the gnomon to enable access to the inner staircases. The instrument has three additional quadrants, two on the west and one on the eastern side of the gnomon.
Jai Prakash Yantra: The Jai Prakash Yantra is composed of two hollow hemispheres, each set into its own platform, about 8.3 meters in diameter. The rim of the hemispheres is parallel to the horizontal plane and open to the sky. Rooms have been carved out of the platform; these spaces, finished with plaster, appear to be either storage or living spaces. The eastern part of the Jai Prakash Yantra has an underground cellar. The instruments have an overall depth of about 5.5 meters, half of which is above the ground while half is sunk. The interior concave surface represents an inverted image of the sky, where the lowest point is the zenith and the rim of the hemispheres is the horizon. The surface is marked with scales to measure the altitude and azimuth of the celestial bodies. The surface is divided into sections and every alternate section is sunk to provide staircases to access the markings and take readings. The spheres are complementary; the hollowed sections in one correspond to the solid sections in the other. This factor in the instrument design enabled nighttime readings of celestial bodies, which was not possible with earlier hemispherical sundials. Cardinal points are marked on the rim of the hemisphere, with cross wires stretched between them. The shadow of the point of intersection of the cross wires falling on the concave surface indicates the location and path of the sun.
Ram Yantra: The Rama Yantra is located towards the southern edge of the site. It is composed of two complementary hollow cylindrical structures that are open to the sky and positioned close to one other along the north-south axis. The instruments are sunk two meters into the ground, so that the observer has to descend into the instrument to take the readings. Each cylinder is prescribed by a three-tiered circular wall, which steps back gradually from the periphery with every rising tier. The wall is about a meter thick at the bottom, narrowing to ca. 60 centimeters at the top, and is punctured at regular intervals of about a meter with keel-arched openings. The openings in the upper two tiers are about 1.5 meters tall and 1 meter tall in the lowest tier. The curved perforated walls describing the perimeter of each cylinder act as thresholds. Each instrument has a vertical pole marking the centre of the cylinder, which is about a meter and a half in diameter, constructed in stone and covered in plaster. The height of the wall and the pillar is equal to the inner radius of the cylinder. Inside the cylinder, a raised red sandstone floor supported on masonry arches is positioned at a height of one meter from the ground. It is divided into equal sectors radiating out from the central pillar. Every alternate sector has been removed to allow access for taking the readings on the solid sectors. The sectors and openings in one cylinder are the inverse of the other. Like the Jai Prakash Yantra, if the two cylinders were superimposed, they would form a complete cylinder. This division of a single instrument into two complementary units was done mainly to facilitate the readings for celestial bodies at night.
The instrument is designed to measure azimuth and altitude. For azimuth measurements, concentric circular scales with their centers on the axis of the cylinder are engraved on the circular slab and the interior of the walls. These are divided into degrees and minutes. The altitude is measured from the equally spaced radial lines drawn on the floor and extending upwards on to the curved walls of the cylinder. The coordinates of the sun are determined by observing the shadow of the pillar on the interior surfaces of the cylinder. The location of the top of the shadow with respect to the semicircular scales indicates the azimuth and the angle of the shadow, with respect to the radiating scales indicates the altitude. In order to record the coordinates of an astronomical object at night, it is sited from within one of the cylinders of the Ram Yantra and aligned with the top edge of the pillar and the point of observation, which indicates the coordinates of the object. In case the vantage point is located on the vertical surfaces of the cylinder, slots have been provided to insert a plank of wood between the piers rising between the openings in the curved walls. The observer could then perch on these planks to take a reading.
All of the instruments are made of stone and were originally covered with limestone plaster. At present they have been finished with brick powder, giving the complex a reddish hue. The scales of the various instruments finished in white plaster, with the exception of the Mishra Yantra, whose scales are white marble. The structures lack any surface decoration or carvings. The keel arches spanning the openings in the Samrat Yantra and the Ram Yantra are Mughal in style. As the movement of the sun creates patterns on the ground and on various surfaces of the instruments, the resulting shadows form an incidental but dominant feature of the architecture of the Jantar Mantar.
Created as a scientific laboratory for observing and analyzing the location and movement of the celestial bodies, the Jantar Mantar instruments were not original or unique in their ability to make such observations; their ingenuity lies in the size and design of the instruments. The use of masonry and plaster for construction rendered the shapes, scaled for human use, monolithic and formal.
Asher, Catherine. The New Cambridge History of India: Architecture of Mughal India. Cambridge: Cambridge University Press, 1992. 300-301.