Res Gestae
Ammianus Marcellinus
Ammianus Marcellinus. Ammianus Marcellinus, with an English translation, Vols. I-III. Rolfe, John C., translator. Cambridge, MA; London: Harvard University Press; W. Heinemann, 1935-1940 (printing).
And after bringing these (as his lofty and serious tasks) to an end, he turned to the exercise of his intellect, and it is unbelievable with what great eagerness he sought out the sublime knowledge of all chiefest things, and as if in search of some sort of sustenance for a soul soaring to loftier levels, ran through all the departments of philosophy in his learned discussions.
But yet,
If, then, it is true (as divers writers report) that King Cyrus and the lyric poet Simonides, and Hippias of Elis, keenest of the sophists, had such powerful memories because they had acquired that gift by drinking certain potions, we must believe that Julian, when only just arrived at manhood, had drained the entire cask of memory, if such could be found anywhere. These, then, were the nightly evidences of his self-restraint and his virtues.