One of the most exquisite of telephone hoaxes known to me was one contrived by Dr Carl Bosch when he was a research student in Germany. He happened to work in a laboratory situated several floors up, where from his window he found that he could survey a block of flats across the road. Having discovered that the occupant of one of the flats was a newspaper correspondent, Bosch telephoned him pretending to be his own professor. Excitedly he explained to the correspondent that he had just invented a marvellous system of television (the date was 1933) which you could clip on to an ordinary telephone set, look into it and see the man that you were speaking to at the other end. Of course, the newspaper man was incredulous. The ‘professor’ then offered to demonstrate the system to him, inviting him to point the telephone towards the middle of his room, then stand in front of it and do anything that he liked, such as standing on one leg, after which the ‘professor’ would tell him what he had done. The result was a rave article in the local newspaper, an embarrassed newspaperman, and an astonished ‘professor’.
— Robert L. Pfaltzgraff et al., Intelligence Policy and National Security, 1981