Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v2.c12.s8.1

v2.c12.s8.1

That the cause of the lunar and solar eclipses is not the demon Rāhu, but the earth's shadow in the case of the lunar eclipse and the moon in the case of the solar eclipse, was known since the times of Varāhamihira and Āryabhaṭa who are the oldest known ‘human’ authors of astronomical works. While declaring that he would describe the cause of the eclipses in such a way as would reconcile the teachings of the Śrutis, Smṛtis and Jyotiṣa Saṃhitā with the astronomical theory, Brahmagupta* observes “Rāhu entering the earth's shadow envelops the moon in the lunar eclipse, and entering the Moon, it envelops the Sun at the time of the solar eclipse”, and Bhāskarācārya** also has explained the phenomena in the same way.