The corpus, every claim citable.

Sūrya-Siddhānta i.30 fixes the Moon's sidereal revolutions per Age at 57,753,336; i.37 fixes the Age's civil days at 1,577,917,828. The implied sidereal month, 27.321674 days, differs from the modern 27.321662 by about 1.1 seconds — roughly 0.5 parts per million. Babylonian-Greek lunar theory reached comparable precision by other routes; the Siddhānta's whole-number encoding is the Indian tradition's own and stayed in computational use for over a millennium.

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

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

Sūrya-Siddhānta xiii (the "astronomical upaniṣad" chapter) directs the teacher to build an armillary sphere — an earth-globe ringed by the circles of the asterisms and ecliptic — explicitly "in order to the instruction of the pupil," then covers other instruments, especially for timekeeping (xiii.17–25). Burgess notes Indian practice paired a meridian circle with the clepsydra, closely analogous to later Western method: the hardware behind the siddhānta's precision parameters.

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

Sūrya-Siddhānta iii builds working astronomy from a gnomon: on a leveled surface, a drawn circle and a twelve-digit vertical stick yield the cardinal directions (from the shadow-tip's morning and evening crossings), the observer's latitude (equinoctial noon shadow, iii.17), and time-of-day quantities. Burgess's commentary works the rules for Washington, D.C. and gets its latitude right. The gnomon procedures are the observational ground floor of the siddhānta's parameter system.

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

Sūrya-Siddhānta iv.1 gives the Moon's diameter as 480 yojanas; with the Earth's diameter fixed at 1,600 yojanas (i.59), the implied Moon-to-Earth size ratio is 0.30, against a true value of 0.27 — accurate to about ten percent. The same verse's solar diameter (6,500 yojanas ≈ 4 Earth-diameters) is too small by a factor of ~27: lunar parallax was within naked-eye reach and solar parallax was not. The accuracy tracks the observable.

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