Aryabhatiya I.6 (499 CE) gives the obliquity of the ecliptic — the angle between Earth's equator and its orbital plane — as 24°. Modern radar measurement is 23.44°. Off by 0.56°, ~2%. But Earth's obliquity oscillates between 22.1° and 24.5° over a 41,000-year cycle, and roughly 5,000 years before Aryabhata wrote, it was much closer to 24°. The value likely reflects accumulated Indian observational tradition from when 24° was correct.