Journalist: - "It might be inconvenient to interrupt our profound discussion and change the subject slightly, but I would like to know whether extraneous, abstract thoughts ever enter your head while playing a game?"
Tal: - "Yes. For example, I will never forget my game with GM Vasiukov on a USSR Championship. We reached a very complicated position where I was intending to sacrifice a knight. The sacrifice was not obvious; there was a large number of possible variations; but when I began to study hard and work through them, I found to my horror that nothing would come of it. Ideas piled up one after another. I would transport a subtle reply by my opponent, which worked in one case, to another situation where it would naturally prove to be quite useless. As a result my head became filled with a completely chaotic pile of all sorts of moves, and the infamous "tree of variations", from which the chess trainers recommend that you cut off the small branches, in this case spread with unbelievable rapidity.
And then suddenly, for some reason, I remembered the classic couplet by Korney Ivanovic Chukovsky: "Oh, what a difficult job it was. To drag out of the marsh the hippopotamus".
I do not know from what associations the hippopotamus got into the chess board, but although the spectators were convinced that I was continuing to study the position, I, despite my humanitarian education, was trying at this time to work out: just how WOULD you drag a hippopotamus out of the marsh? I remember how jacks figured in my thoughts, as well as levers, helicopters, and even a rope ladder.
After a lengthy consideration I admitted defeat as an engineer, and thought spitefully to myself: "Well, just let it drown!" And suddenly the hippopotamus disappeared. Went right off the chessboard just as he had come on ... of his own accord! And straightaway the position did not appear to be so complicated. Now I somehow realized that it was not possible to calculate all the variations, and that the knight sacrifice was, by its very nature, purely intuitive. And since it promised an interesting game, I could not refrain from making it."
Journalist: - "And the following day, it was with pleasure that I read in the paper how Mikhail Tal, after carefully thinking over the position for 40 minutes, made an accurately-calculated piece sacrifice".
Mikhail Tal, The Life and Games of Mikhail Tal