@KoiwiGal - I don't think you give people enough credit. The kind of mathematics they were doing thousands of years ago was certainly advanced enough to calculate torsional stiffness.
Think about what the Chinese, for example, accomplished centuries before Western civilizations.
They had advanced hydraulics and mechanical systems. Those would have certainly needed the torsional stiffness formula in order to get past a certain point.
People always underestimate what their ancestors were capable of.