The chessboard on the top of the box was thin. This allowed for a magnetic linkage. Each piece in the chess set had a small, strong magnet joined to its base. When placed on the board the pieces would attract a magnet attached to a string under their places on the board. The person inside the machine could see which pieces moved where on the chess board. The bottom of the chessboard was also numbered, 1–64, allowing the person to see which places on the board were affected by a player's move. The magnets were placed so that they were not affected by any magnets outside the box. Kempelen would let people from the audience put a large magnet next to the board to show that the machine was not influenced by magnetism.