Napier's Bones

Napier's Bones are John Napier's most famous tool and were used for calculation for hundreds of years.

Napier's Promptuary

Napier's developed his Promptuary from his bones to allow calculations to be done without the need to draw a grid and do extra working.

Napier's Local Arithmetic uses a Chess Board and counters to multiply. It uses the same Binary arithmetic used by computers.