The corpus, every claim citable.

Surya-Siddhanta III.9 (~5th c. CE) gives 600 equinoctial revolutions per mahayuga (4,320,000 years) — ≈50 arcseconds per year, close to the modern 50.3″/yr. Whether the motion is monotonic (progressive precession) or oscillatory (libration/trepidation between ±27°) is ambiguous: III.11-12 suggest libration, III.9 alone reads as progression. Burgess 1860 reads libration; modern scholarship leans toward original progression later edited for libration.

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