Hiero II of Syracuse

In the meantime, the Mamertines, a body of mercenaries from Campania who had been employed by Agathocles the late tyrant of Syracuse, had seized the stronghold of Messina, and proceeded in harassing the Greeks around them.

[3] Hiero at once joined the Punic leader Hanno, who had recently landed in Sicily; but fighting a battle to an inconclusive outcome with the Romans led by the consul Appius Claudius Caudex, he withdrew to Syracuse.

[5] He kept up a powerful fleet for defensive purposes, and employed his famous kinsman Archimedes in the construction of those engines that, at a later date, played so important a part during the siege of Syracuse by the Romans.

Supposedly, it was while noticing the rise in water level when getting a bath tub that Archimedes realized he could use water-displacement to measure the crown's irregular shape, and in his excitement about the discovery he dashed outside cheering and forgot to dress himself first.

Vitruvius concludes this story by stating that Archimedes' method successfully detected the goldsmith's fraud; the smith had indeed taken some of the gold and substituted silver instead.