Aulus Gellius, Attic Nights, 1.1
The way that Socrates developed the endurance of his body; and also on the temperance of that man.
“Among the voluntary actions and bodily exercises for enhancing his endurance against any possible event, we have heard that Socrates used to do this regularly: it is reported that Socrates was in that habit of standing all day long in one position, from the first shine of light one day until the next sunrise, without moving from the same footprints, keeping his eyes directed in a single place and in deep thought, as if his mind and spirit were separated from his body. This is why, when Favorinus was mentioning the strength of that man and his other qualities, he added: “He often stood from sunrise to sunrise, more solid than tree-trunks” (fr. 97.1).
His temperance was so great, as it is reported, that he lived his entire life with uncompromised health. Even during the ruin of that plague, which at the beginning of the Peloponnesian war destroyed the Athenian state with an unknown type of disease, he is said to have avoided the dangers of pleasure and to have maintained the health of his body with his habits of abstention and moderation to such a degree that he was not at all afflicted by the disaster touching everyone else.”
Quo genere solitus sit philosophus Socrates exercere patientiam corporis; deque eiusdem viri temperantia.
1 Inter labores voluntarios et exercitia corporis ad fortuitas patientiae vices firmandi id quoque accepimus Socraten facere insuevisse: 2 stare solitus Socrates dicitur pertinaci statu perdius atque pernox a summo lucis ortu ad solem alterum orientem inconivens, immobilis, isdem in vestigiis et ore atque oculis eundem in locum directis cogitabundus tamquam quodam secessu mentis atque animi facto a corpore. 3 Quam rem cum Favorinus de fortitudine eius viri ut pleraque disserens attigisset: πολλάκις ἐξ ἡλίου εἰς ἥλιον εἱστήκει ἀστραβέστερος τῶν πρέμνων (Fav. Fr. 97.1).
4 Temperantia quoque fuisse eum tanta traditum est, ut omnia fere vitae suae tempora valitudine inoffensa vixerit. 5 In illius etiam pestilentiae vastitate, quae in belli Peloponnesiaci principis Atheniensium civitatem internecivo genere morbi depopulata est, is parcendi moderandique rationibus dicitur et a voluptatum labe cavisse et salubritates corporis retinuisse, ut nequaquam fuerit communi omnium cladi obnoxius.
Earlier in the Attic Nights Aulus reports a difference type of exercise to keep the philosopher sharp.