The Astronomical Observatories of Jai Singh c4.s1.15

c4.s1.15

(iii) The Hindu name for the astrolabe is *Yantra Rāja* and Garrett says³ that this "appears to be a very ancient type of instrument of Hindu origin," and also that "it appears to have been held in great esteem by Jai Singh as he himself wrote a book concerning its construction and use." As a matter of fact, the astrolabe or *Yantra Rāja* is not of Hindu origin at all. The earliest Hindu work on this instrument is of the fourteenth century of our era, while numerous Arabic and Persian works dating from the tenth century onwards are known. The earliest Hindu work known is by Mahendra Sūri and was written in the time of Firoz Shah in Śaka 1292 or A.D. 1370,⁴ and there are indications that it was used by Jai Singh. But Jai Singh did not rely on this work alone and certainly used some of the Arabic or Persian text-books on the astrolabes, of which there were a great many available.