.

until I found myself beginning to believe that that possibility could be accomplished.

Whereupon, realizing that there, too, lay madness, I forwent the squaring of the circle, although I assure you it required a considerable sacrifice on my part, for the mental exercise involved was a splendid time-killer.
By sheer visualization under my eyelids I constructed chess-boards and played both sides of long games through to checkmate.

But when I had become expert at this visualized game of memory the exercise palled on me.

Exercise it was, for there could be no real contest when the same player played both sides.