The treatise On the Equilibrium of Plane hugely influenced the birth of modern science. In its two books, Archimedes demonstrates the fundamental Law of the Lever which is central to all statics: there is equilibrium in a lever when the weights are inversely proportional to the distances from the fulcrum.

If a person positions themselves at the right point on the longer arm of the model, they can balance a heavier person on the shorter arm.