Earth’s obliquity

Observing, and comparing, the summer and winter solstice, one could seemingly ascertain the earth’s obliquity, by noting the angular displacement associated with the rising sun, and where it intersects the horizon, such as for along a ridge. Such angular displacement would be double the current obliquity of ~23.4 degrees. The differing trajectory for the sun in winter and summer was easily noted; in fact comparing respective trajectories at noon should also give an angular displacement double the obliquity. American Indians probably just noted differences in rising sun location for winter and summer etc. Ancients observed differences in shadows.  TMM

http://en.wikipedia.org/wiki/Obliquity.