In puero statim corporis animique dotes exsplenduerunt, magisque ac magis deinceps per aetatis gradus: forma egregia et cui non minus auctoritatis inesset quam gratiae, praecipuum robur, quamquam neque procera statura et ventre paulo proiectiore; memoria singularis, docilitas ad omnis fere tum belli tum pacis artes. armorum et equitandi peritissimus, Latine Graeceque vel in orando vel in fingendis poematibus promptus et facilis ad extemporalitatem usque; sed ne musicae quidem rudis, ut qui cantaret et psalleret iucunde scienterque. e pluribus comperi, notis quoque excipere velocissime solitum, cum amanuensibus suis per ludum iocumque certantem, imitarique chirographa quaecumque vidisset, ac saepe profiteri maximum falsarium esse potuisse.
(Suetonius, Div. Tit. 3)
His qualities of mind and body at once stood out even when he was a boy but still more so as he advanced towards maturity. His appearance was striking, conveying authority as well as charm, and he was unusually strong, though not tall in stature, while his stomach protruded a little. He had an exceptional memory and a great gift for acquiring almost all the arts of war as well as those of peace. He was highly skilled in the use of weapons and in horsemanship and had a ready fluency in both Latin and Greek to such a degree that he could make a speech or compose a poem without preparation. Even in music he was not without talent and could sing and play the cithara with grace and skill. I have discovered from a number of sources that he used to write shorthand at great speed and for fun would play at competing with his secretaries and that he could imitate any handwriting he had seen and often confessed he could have been the greatest of forgers. (tr. Catharine Edwards)