An attempt to devise quicker methods of calculation by the use of rudimentary calculating devices, including "Napier's bones," a set of ten rods of wood or ivory. Other methods include the "aereal abacus," consisting of a checkerboard with counters expressing numbers in the binary scale, and the "promptuary" or "lightening calculator." This "deals with a more complicated system of multiplication by engraved rods and strips, which has been called the first attempt at the invention of a calculating machine" (DSB).