Lord of the flies

It is often said that the great chessboard artist, Polish Grandmaster Akiba Rubinstein, was afflicted during tournament play by an imaginary fly, which he sought in vain to swat away. As is the nature of imaginary beings, a case in point is the A Bao A Qu, the first entry in the bible of such entities, The Book of Imaginary Beings by Jorge Luis Borges, they remain undetectable to the uninitiated. The A Bao A Qu, of course, lived invisibly on the stairway of the Tower of Victory in Chittor, Rajasthan, imperceptible to all but those who had attained perfect Nirvana. It was not widely seen.
 
Similarly, the offending fly was visible only to poor, distracted Rubinstein. The wise of the time saw in this the incipient lunacy which was to cause him to abandon chess for the three decades remaining to him after his last major tournament, the Chess Olympiad of Prague, 1931.