The engineer Coleman Sellers questioned the origin and weight of the board used with the balance spring apparatus. Sellers wrote that a standard mahogany board weighs around thirteen and half pounds but the one used in Crookes' experiment may have been at fault at only six pounds. Crookes responded to Sellers claiming the board weighed six pounds and this was not a mistake, he also stated he had the board for about sixteen years and it was originally cut in a lumber yard.