Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v2.c12.s3.3

v2.c12.s3.3

It has already been told (page XXXI of Part I) that the motion of planets in their orbits has been assumed to be the same, and it is about 11858¾ yojanas in one day. And it is also assumed that each planet travels in one Kalpa a length equal to the circumference of the celestial sphere. In other words, the length of the celestial orbit* is equal to the sum of the orbital lengths of the revolutions made by each planet in one Kalpa. Hence, the length of a planet’s orbit is obtained by dividing the length of the orbit of the celestial sphere by the number of revolutions made by each planet in one Kalpa. The Sūrya Siddhānta gives the measures of orbital lengths as follows :—