Let me tell you two stories.
For the first, we go back to Syracuse, Sicily, in the third century B.C.
Archimedes, a Greek mathematician, physicist, and inventor, was called before the throne to solve a difficult problem. The king had ordered a pure gold crown from the local goldsmith. But when the crown arrived, the king suspected the goldsmith of keeping some of the gold and replacing it with silver. The king asked Archimedes to help him prove it.