Jantar Mantar is the largest of the five observatories built by Sawai Raja Jai Singh. Located in the city of Jaipur, Jantar Mantar draws its name from Sanskrit terms 'yantra' and 'mantra'. The former term means instrument while the latter means formulae. Built between the period of 1728-34, the Jantar Mantar is based on the astronomical studies conducted by Sawai Jai Singh and his men around the world. One of his men brought a manual which was a copy of La Hire's "Tables". Accordingly, Jai Singh ordered the construction of the observatories based on the information provided in this manual. Jai Singh had to make choice regarding the material used for the construction of the observatory. He had the option of using either metal or masonry instruments and he preferred the latter to the former. Infact, he himself designed the stone and masonry instruments of the observatory.