Yantraraja

It is also the title of a Sanskrit treatise on the construction and working of the astrolabe composed by a Jain astronomer Mahendra Sūri in around 1370 CE.

The earliest crude forms of the instrument are believed to have been constructed during second century BCE in Greece.

The earliest extant astrolabe constructed in India, now in a private collection in Brussels, is dated 1 February 1601.

With the support and patronage of Firuz Shah Tughlaq, Mahendra Sūri, a Jain astronomer composed the first ever Sanskrit manual on astrolabes.

The fourth chapter Yantrasodhanādhyāya discusses method for ascertaining whether the astrolabe has been properly constructed.

Over the centuries since the publication of Mahendra Sūri's Yantrarāja in 1370, several other Sanskrit manuals on the astrolabe have been composed.

An astrolabe from the Mughal era exhibited at the National Museum in New Delhi, India.
Front of an Indian astrolabe now kept at the Royal Museum of Scotland at Edinburgh. ( (Internet Archive) )
Image of folio 3 of Malayendu Sūri's commentary (1382) on Mahendra Sūri's Yantrarāja (1370). (Internet Archive)