King Theron of Tyre summoned the great Greek mathematician, Archimedes, to solve a problem. An artisan had constructed a "gold" crown for him, but some one suggested that it might be, say, lead underneath. The King wished Archimedes to determine a way to test this suspicion.

Archimedes thought about the problem for several days without solution. One day, as was his custom, he went to the public baths. As the custom after bathing, he oiled his body. As was his quaint custom, he drew geometric exercises on his body. These he would wash off in he bath. This time, noticing how the water level rose as he slid into the pool, he had a great idea.

Rushing out of the water and out onto the street, the great Archimedes ran nakedly streaking down the street, allegedly crying, "Eureka!", meaning, "I've found it!".

Archimedes realized that EACH BODY DISPLACEMENT A MAS OF WATER EQUAL TO HIS OWN MASS. Since the masses of units of lead and gold are markedly different, this was a way of determining the difference in composition of a crafted body.

(History records that the crown was not pure gold.)

Physics teachers have an instrument, sometimes called "An Archimdean Floation Device", used to teach physics students about this important and useful principle of physics.