koko and the jumping block\nshort cube a libre routine with a jack-in-the-box\nrobert lotz
1945/27
tarbell course in magic — volume 4 Robert Lotz
mental blocks\nspectator and performer put different colored cubes in a tube, same order, both blindfolded\njames auer
1961
still more miracles in mentalism James Auer
Mental Blocks
spectator and performer put different colored cubes in a tube, same order, both blindfolded