All The Napiers
I have a set of Napier Bones and they are amazingly cool for teaching and putzing with math. What I did not know were the other devices Napier came up with for the task of doing maths. This one site gives you all you need to start your journey using Bones, Promptuary and Local Arithmetic. Dive in and enjoy.
This site is dedicated to the Mathematical Calculation Tools Developed by John Napier."