The first-century inventor and scientist Archimedes is remembered by physicists as the originator of the principles of mechanics, buoyancy, the lever and the pulley, according to Famousscientists.org. Perhaps his best-known contribution to physics is his discovery of the principle of displacement, which states that objects displace a volume of water equal to their own weight.
Archimedes lived in Syracuse between 287 and 212 BCE. During his life, Archimedes advanced the human understanding of physics by developing the fields of hydrostatics and statics, as well as improving the understanding of the lever, according to Wikipedia. The scientific model that bears his name, the Archimedes Principle, was developed as a way to determine the purity of gold. Using the principle of displacement, Archimedes devised a test whereby a "gold" crown was submerged in water and the volume displaced was recorded. An equal measure, by weight, of pure gold was then subjected to the same test. If the crown had been made of gold, it would have been expected to displace the same amount of water as the gold ingot. In the event, the crown displaced more water than the gold, thus demonstrating that it was less dense than gold and had therefore likely been alloyed with silver.