2000 years ago, a Greek king Hiero ordered a gold crown. Later,
he heard that the goldsmith substituted some gold with silver,
and kept gold. The king ordered to weight the crown. It weighted
just as much as the gold the king has given to the goldsmith.
It looked like it was made of pure gold. Still the king felt uneasy
about the new crown. To find out the truth, he sent for Archimedes,