I remeasured the grinding stone, after years of it just lying around. Turns out that my original findings were off a little bit. The angle of the top cut from horizon is actually between 29-30 degrees, which marks winter solstice midday at 37.12 degrees N latitude. When the stone is rolled backwards so the top becomes the bottom and the two corners become marking points, those points signify important junctions in any given year’s cycle. That is, when the stone is upright and facing southward, allowing the sun to cast its shadow. See images below.
Unify the Nations – IndianRock.art