Cornelius Nepos
Herodotus does not estimate the size of the Persian army, only saying that they formed a "great and well-furnished army". Among other ancient sources, the poet Simonides, a near-contemporary, says the campaign force numbered 200,000, while a later writer, the Roman Cornelius Nepos estimates 200,000 infantry and 10,000 cavalry. Plutarch and Pausanias both independently give 300,000, as does the Suda dictionary; Plato and Lysias assert 500,000; and Justin 600,000.