<P> A puzzle mug is a mug which has some trick preventing normal operation . One example is a mug with multiple holes in the rim, making it impossible to drink from it in the normal way . Although it is tempting to grasp the body of the mug covering the visible holes and drink the liquid in the usual manner, this would pour the liquid through hidden perforations near the mug's top . The solution is to cover the holes in the rim with hands, but to drink not through the top, but through a "secret" hole in the hollow handle . </P> <P> A puzzle mug called fuddling cups consists of three mugs connected through their walls and handles . The inner holes in the mugs walls are designed in such a way that the mugs must be emptied in a unique sequence, or they will drain . </P> <P> The Pythagorean cup (see picture) contains a small siphon hidden in a rod placed in the mug center . The cup holds liquid if filled below the height of the rod, but once filled above that level, it drains all liquid through the siphon to a hole in its base . </P> <P> Thermochromic mugs change appearance when a hot beverage is poured into them . </P>

What is the bottom of a cup called