Caesar (17.2-17.3)

Now, at his love of danger his men were not astonished, knowing his ambition; but that he should undergo toils beyond his body’s apparent power of endurance amazed them, because he was of a spare habit, had a soft and white skin, suffered from distemper in the head, and was subject to epileptic fits, a trouble which first attacked him, we are told, in Corduba.

Nevertheless, he did not make his feeble health an excuse for soft living, but rather his military service a cure for his feeble health, since by wearisome journeys, simple diet, continuously sleeping in the open air, and enduring hardships, he fought off his trouble and kept his body strong against its attacks. Most of his sleep, at least, he got in cars or litters, making his rest conduce to action, and in the day-time he would have himself conveyed to garrisons, cities, or camps one slave who was accustomed to write from dictation as he travelled sitting by his side, and one soldier standing behind him with a sword.