On Yuan Chwang's Travels in India, 629–645 A.D. v1.c8.s1.26

v1.c8.s1.26

The unceasing revolutions of mortals' existences are a dark long night; were there not a warden of the dawn they would be like the night with its lights which succeeds the setting of the sun; although the night have the light of the stars that is not to be compared to the light of the clear moon. Hence probably India was likened to the moon as [since the sun of the Buddha set] it has had a succession of holy and wise men to teach the people and exercise rule as the moon sheds its bright influences,—on this account the country has been called Yin-tu.