„Nilakantha Somasutvan, the renowned astronomer of the Kerala School, carried out a major revision of the older Indian planetary model for the interior planets, Mercury and Venus, in his treatise Tantrasangraha (1500 AD), and for the first time in the history of astronomy, he arrived at an accurate formulation of the equation of centre for these planets. He also described the implied geometrical picture of planetary motion, where the five planets – Mercury, Venus, Mars, Jupiter and Saturn – move in eccentric orbits around the Sun, which in turn goes around the Earth. The later astronomers of the Kerala School seem to have by and large adopted the planetary model developed by Nilakantha.“ aus: K. Ramasubramanian, M. D. Srinivas, M. S. Sriram: Modification of the earlier Indian planetary theory by the Kerala astronomers (c. 1500 AD) and the implied heliocentric picture of planetary motion. in: Current Science. 10/1994, S. 784–790.
