The Jantar Mantar is an equinoctial sundial which is used to show the time in the daily duration and its consisting of a gigantic triangular gnomon with the hypotenuse parallel to the Earth’s axis. On both side of the gnomon is a quadrant of a circle, parallel to the plane of the equator. The instrument is used to measure the time of day, correct for half a second and declination of the sun and the other heavenly bodies.
There are five Jantar Mantar monuments presents in India, of which the largest is in Jaipur which features many instruments along with the world’s largest stone sundial.The Vrihat Samrat Yantra is a sundial that can give the local time to an accuracy of 2 seconds. It is also defined by UNESCO World Heritage Site.
As in the 18th century, Maharajas Jai Singh II of Jaipur constructed five Jantar Mantars in total, in New Dehli, Jaipur, Ujjain, Matura and Varanasi and all were completed between the duration of 1724 and 1735.
The Jantars have evocative names like Samrat Yantra, Jai Prakash, Ram Yantra and Niyati Chakra; each of them is used to various astronomical calculations. The main purpose of the observatory was to compile astronomical tables and predict the times and movements of the Sun, Moon, and planets.