These little pottery mugs are sold on the Greek Island of Samos (and elsewhere of course) and are based on a design that is supposedly about 2,500 years old. A simple piece of physics, although slightly deeper in philosophical terms.
The cup looks normal, except that there is a central column inside the cup. If you pour water or wine into the cup, you can then drink it in the normal way. However you have to be careful when filling the cup. This particular model has a line marked on the inside. If you fill the cup beyond this line, the cup will empty - every drop will drain out from a hole in the bottom, and you won't get a drink at all.
The cup is attributed to the Greek philosopher Pythagoras, who lived on the Island of Samos 2,500 years ago. As he wrote nothing himself, we only know about Pythagoras from the writings of other people, especially Plato. However as well as his fame as a mathematician, he is also celebrated for his philosophy and his way of life. The Pythagoras Cup illustrates a point that we should not ask for more than our share in life.