This officer, “magister memoriæ,” was a private secretary of the emperor, and had, among other privileges of his office, the right of granting liberty to private individuals to travel by the imperial conveyances along the great highways connecting Rome with the remotest boundaries of the provinces. See Suetonitis, Vita Augusti, chap. xlix., and Pliny, Letters, Books x.-xiv., and Codex Justiniani, Book xii. Title 51.