From the introduction: In the Columbia Teachers College/COMAP Mathematical modeling handbook, one of the modules, “Stable table," concerns this topic: If a typical four-legged table on a continuous but irregular floor has only three legs that are on the floor, it is not necessary to use a folded napkin or other prop to stabilize it. You can rotate the table, and there will be a stable position within a rotation of at most 900 stable, but not necessarily horizontal.