In no other human being have I ever seen such physical endurance. . . . many a time, far in the night, when I was ready to drop with exhaustion, he was still as fresh and buoyant and eager for the game as at the moment of beginning. He smoked and smoked continually, and followed the endless track around the billiard-table with the light step of youth.
The fine billiard table, a gift from Emilie Rogers (wife of Henry H. Rogers), was installed at his home on Fifth Avenue. He reported to Mrs. Rogers:
The billiard table is better than the doctors. It is driving out the heartburn in a most promising way. I have a billiardist on the premises, & I walk not less than ten miles every day with the cue in my hand. . . . The games begin right after luncheon, daily & continue until midnight, with 2 hours intermission for dinner & music. And so it is 9 hours' exercise per day, & 10 or 12 for Sunday.
Clemens did not like to lose. Paine described his behavior on one occasion:
Once, when he found it impossible to make any of his favorite shots, he became more and more restive, the lightning became vividly picturesque as the clouds blackened. Finally, with a regular thunder-blast, he seized the cue with both hands and literally mowed the balls across the table, landing one or two of them on the floor.