Albert Bigelow Paine,
The Boys' Life of Mark Twain — Chapter 15
(1916)
“ His early gaiety came back, but his face had taken on the serious, pathetic look which from that time it always wore in repose. Less than twenty-three, he had suddenly the look of thirty, and while Samuel Clemens in spirit, temperament, and features never would become really old, neither would he ever look really young again. ”
