http://agathe.gr/democracy/practice_of_ostracism.html
Ostracism Soon after their victory over the Persians at the battle of Marathon in 490 B.C., the Athenians began the practice of ostracism, a form of election designed to curb the power of any rising tyrant ... Max. dim.: 0.11 m. Athens, Agora Museum P 14490. ... Max. dim.: 0.073 m. Athens, Agora Museum P 6107. ... Max. dim.: 0.07 m. Athens, Agora Museum P 16755.