Plutarch, Cato the Younger
Bernadotte Perrin, Ed.

56. Conjecturing, now, that Pompey the Great would make his escape into Egypt or Libya, and being eager to join him, Cato put to sea with all his company and sailed away, after first giving those who had no eagerness for the expedition leave to depart and remain behind. After reaching Libya, and while sailing along its coast, he fell in with Sextus, the younger son of Pompey, who told him of his father's death in Egypt. [2] All, of course, were deeply distressed, but no one, now that Pompey was gone, would even listen to any other commander while Cato was at hand. For this reason also Cato, who had compassion on men who were brave and had given proof of fidelity, and was ashamed to leave them helpless and destitute in a foreign land, undertook the command, and went along the coast to Cyrene, the people of which received him kindly, although a few days before they had closed their gates against Labienus.¹ [3] There he learned that Scipio, the father-in-law of Pompey, had been well received by Juba the king, and that Attius Varus, who had been appointed governor of Libya by Pompey, was with them at the head of an army. Cato therefore sent out thither by land in the winter season, having got together a great number of asses to carry water, and driving along with him many cattle. Besides, he took with him chariots, and the people called Psylli.² These cure the bites of serpents by sucking out the venom, and charm and deaden the serpents themselves by means of incantations. [4] Though the march lasted for seven days consecutively, Cato led at the head of his force, without using either horse or beast of burden. Moreover, he used to sup in a sitting posture from the day when he learned of the defeat at Pharsalus; yes, this token of sorrow he added to others, and would not lie down except when sleeping. After finishing the winter in Libya, he led forth his army³; and it numbered nearly ten thousand.