India

To the north-west of the Prakash Yantra, there is a structure or instrument called Mishra Yantra.Maharaja Jai Singh was a fanatical astronomer himself who studied various works from Hindu, Muslim and European astronomy. It consists of five instruments. Pillars on the southwest of Mishra Yantra are used to measure the shortest day (21 December) and the longest day (21 June) of the year. 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. Having said that, we must give accreditation to the Jantar Mantar for its scientific acumen which could have reaped more fruits had there been appropriate motivation and resource given for research and development. It is no denying the fact that the structure does represent the scientific heritage of India, though not being used in the modern scientific research.When compared to others, this observatory is the largest and the best preserved today. But, after its erection in 1724, it remained functional only for seven years. Observations made each day were noted down and later a chart called Zij Muhammad Shahi was prepared. This was then dedicated to the reigning monarch. Many experts in this field are of the view that these observatories fell into disuse, because of lack of thought on the part of the king. The original name Yantra (instrument) mantra (formula) has been corrupted to Jantar Mantar.
Some of the major instruments at Jantar Mantar Delhi are given bellow: