The year is about 1610; the place is Merchiston Castle near Edinburgh, Scotland; and the Baron of the castle, John Napier, is sitting at his desk working on his latest invention — logarithms. The computation of all of the tables of logarithms involved required many calculations, which had to be correct. Napier, ever the inventor, realized that his need to be able to calculate correctly, as well as the needs of many others at this time, made instruments that would mechanically compute of special interest. So … Napier picked up his bones (or rods as they were sometimes called) and started calculating.

It is not known when John Napier had his idea for “rod reckoning”, a mechanical means to multiply, divide, square root and cube root numbers. He had started a manuscript about algebra and arithmetic, called De arte logistica, but put this work aside when he started working on logarithms (Napier's incomplete De arte logistica was not published until 1839). John Napier published Mirifici logarithmorum canonis descripto in 1614, with an English translation published in 1616. His next work was Rabdology, which was published in 1617. It is thought that the word Rabdology was a combination of Greek words meaning rod reckoning.

Napier's “bones” were not meant to replace paper and pencil, but to reduce the amount of time spent calculating and diminish errors in the calculations of products, quotients, square roots and cube roots.