Surya Siddhanta
कल्पोक्तचन्द्रभगणा गुणिताः शशिकक्षया । आकाशकक्षा सा ज्ञेया करव्याप्तिस् तथा रवेः॥
If the stated number of revolutions of the moon in an Man (kalpa) be multiplied by the moon's orbit, the result is to be known as the orbit of the ether : so far do the rays of the sun penetrate.
english translation