Eerily Perfect Ancient Egyptian Bowl

This little granite bowl has a secret. Just 9 inches wide, it balances perfectly on 0.15 square inches!

The top rests horizontally when the bowl is placed on a glass shelf. That’s only possible because the entire bowl has a symmetrical wall thickness, no part  thicker or thinner than the rest. Any asymmetry would cause a lean. This amount of precision is difficult in today’s machine age – how were they able to do it in ancient Egypt?