Hundreds of carved stone spheres, roughly three inches in diameter, believed to date to around 2000 BC, have been found over the years in Scotland. Many are carved with lines corresponding to the edges of regular polyhedra. Some of these depict the five platonic solids, as illustrated, long before the greeks wrote about them. As to the purpose of the stone balls – no one knows. Perhaps they were used as weights, as dice for oracles, in ball games, or just as ‘prestige objects’. Or maybe the neolithic people were interested in sacred geometry.
More from wikipedia here. There’s also an interesting article on THE GEOMETRY OF CREATION, Plato’s Timaeus and the Regular Polyhedra here, and more stone balls images at the Modern Antiquarian.