At first sight, the Jantar Mantar appears like a gallery of modern art. It is, however, an observatory. Sawai Jia Singh II of Jaipur (1699-1743), a keen astronomer and a noble in the Mughal court, was dissatisfied by the errors of brass and metal astronomical instruments.Under patronage from the emperor, he set on himself the task of correcting the existing astronomical tables and updating the almanac with more reliable instruments. Delhi’s Jantar Mantar is the first of the five observatories that he built with large masonry instruments.
The observatory has the Samrat Yantra, a simple equal hour sun dial, the Ram yantra for reading altitudinal angles; Jai Prakash for ascertaining the position of the sun and other celestial bodies, and the Misra Yantra which is a combination of four scientific gadgets.
courtesy : knowindia.gov.in