While he (Sandrocottus [Chandragupta]) was lying asleep, after his fatigue, a lion of great size having come up to him, licked off with his tongue the sweat that was running from him, and after gently waking him, left him. Being first prompted by this prodigy to conceive hopes of royal dignity, he drew together a band of robbers, and solicited the Indians to support his new sovereignty. Some time after, as he was going to war with the generals of Alexander, a wild elephant of great bulk presented itself before him of its own accord, and, as if tamed down to gentleness, took him on its back, and became his guide in the war, and conspicuous in fields of battle. Sandrocottus, having thus acquired a throne, was in possession of India, when Seleucus was laying the foundations of his future greatness; who, after making a league with him, and settling his affairs in the east, proceeded to join in the war against Antigonus. As soon as the forces, therefore, of all the confederates were united, a battle was fought, in which Antigonus was slain, and his son Demetrius put to flight.
— Marcus Junianus Justinus, 2nd-century CE, Epitome of the Philippic History of Pompeius Trogus, Book XV, Translator: John Selby Watson, XV.4.19