The corpus, every claim citable.

Sūrya-Siddhānta XII.53 (c. 400–500 CE core text, Burgess 1860 translation) states that the Earth is a globe in space with no absolute up or down: every observer takes their own place to be uppermost. Verses 51–52 apply it concretely — dwellers at opposite points of the globe each suppose the other underneath. Greek astronomy established terrestrial sphericity earlier (Aristotle, c. 350 BCE); the Siddhānta's plain statement of the relativity of "up" is among the clearest in any ancient text.

Translation of the Surya-Siddhanta · tr. Ebenezer Burgess, 1860