Eureka

Eureka!, is from the Greek meaning ‘I have found it’. It is the phrase uttered by the Greek inventor and Mathematician Archimedes (287-212 BCE), when he invented his Principle that the Mass of an object divided by its Volume would equal its Density.
He was then able to calculate whether the density of a crown was made of Gold or of a lighter metal without cutting it open.

Vitruvius tells the story of how Archimedes invented a method to determine the volume of a body having an irregular shape.
King Hiero II of Syracuse had commissioned a crown to be made out of solid Gold. However, He distrusted the Goldsmith and asked Archimedes to find a way of calculating whether he had used cheaper silver instead, but without Archimedes melting down the crown.
Whilst getting into his bath, Archimedes observed that as he got in, the water level rose.
He realised that the crown would displace a quantity of water equal to its own volume.
Archimedes concluded that the Mass of the crown divided by its Volume would equal its Density, and he could then calculate whether it was the density of Gold or of a lighter metal.
In his excitement he leapt out of his bath and ran naked down the street to the King, shouting Eureka! (I have found it!).
The test was carried out and it showed that silver had been added.