Rainich was giving a lecture in which he made use of a clever trick which he had discovered. Someone in the audience indignantly interrupted him pointing out that this was the famous Rabinowitsch trick and berating Rainich for claiming to have discovered it. Without a word Rainich turned to the blackboard, picked up the chalk, and wrote

RABINOWITSCH

He then put down the chalk, picked up an eraser and began erasing letters. When he was done what remained was

RA IN I CH

He then went on with his lecture.