Yantrarāja: The Astrolabe Comes to Sanskrit
How a Jain monk at the Delhi court put the 'king of instruments' into Sanskrit verse in 1370, and how India's own ring instruments met it
Around 1370, at Fīrūz Shāh Tughluq's court, the Jain monk Mahendra Sūri wrote the Yantrarāja, the first Sanskrit manual on the astrolabe. Learn how the instrument flattens the sky onto a brass plate, how Mahendra named every part in Sanskrit, how India's own ring instruments met it, and how Indian makers changed it in brass.
A Brass Disc at Firozabad
It is around the year 1370, in Firozabad, the new capital that Sultan Fīrūz Shāh Tughluq had begun building on the bank of the Yamuna in 1354. High on one of its palace buildings stands a polished Aśokan pillar the Sultan had brought all the way from Topra, in present-day Haryana. Somewhere below it, a Jain monk named Mahendra Sūri is studying a round brass instrument. It is heavy and cool in the hand. Its face carries a lattice of curved brass pointers, each tip marking a star. Its plates are cut with fine circles and letters in Arabic script.
The chronicles do not record the room or the hour. They record the task. The Sultan loved this instrument, the astrolabe. Persian chroniclers say he had several made in Delhi, including a splendid one named after himself. Now he wanted it explained in Sanskrit, so that the astronomers of the land could build it and use it too.
That was the stake. The astrolabe came from a Greek and Arabic tradition. Its parts, its maths and its words had never been written in an Indian language. If the manual failed, the brass disc would stay a palace curiosity. Could a monk trained in the Sanskrit siddhāntas turn it into Sanskrit verse? What Mahendra wrote was still being copied, and cast in brass, more than two centuries later.
The Sky, Flattened onto a Plate
The idea behind the astrolabe is Greek. Take the dome of the sky and press it flat onto a disc, in a way that keeps every circle a circle. Greek astronomers worked out this projection. The oldest surviving manual on the instrument was written by John Philoponus of Alexandria around 530 CE. Astronomers of the Islamic world kept it, improved it, and carried it west to Spain and east towards India.