401 BC Xenophon sneezes
If anyone tries to tell you that the ancient Greeks were a people governed by reason and that rationality fled the world when Christianity began to dominate western civilization, refer them to the events described here by Xenophon in his Anabasis.
Xenophon, a young aristocratic Athenian and student of Socrates, joined a Spartan-led army in the pay of the Persian prince Cyrus the Younger who was attempting to seize the throne from his brother Artaxerxes II. When that attempt failed with the death of Cyrus and the murder of the Greek generals, Xenophon urged his fellow mercenaries to fight their way home rather than submit to the humiliating and dangerous terms offered by the Persians.
Xenophon in particular, having armed himself with a splendor becoming his present rank, endeavored to inspire sentiments of honor; and fortunately the favorable omen of sternutation occurred in the midst of his speech; on which the soldiers, all with one accord, worshipped Jupiter the Preserver, from whom the omen was reputed to proceed; and Xenophon breaking off his harangue, proposed a sacrifice to the god, desiring those who approved of the motion to hold up their hands: the show of hands being unanimous, the sacrifice was formally vowed, and a hymn sung; after which he resumed his discourse, and at great length set before the army, now full of hope and cheerfulness, the system which they must adopt to insure a safe and honorable return to their native country.
Thus, an inadvertent sneeze was perceived as having been sent from the gods, and was taken as an omen which helped Xenophon persuade the Greeks to follow his proposals. It should also be noted that when Xenophon had asked Socrates whether he should agree to serve against Artaxerxes, the philosopher did not use reasoned argument to come to a conclusion but recommended that his student consult the oracle at Delphi.