Creative Crafthouse Napiers Bones - Base, Cover and 2 Full Sets of Rods - Math Calculator From 1617 by John Napier Invented by John Napier, Scottish mathematician, in 1617. In common use for nearly 3 centuries as a math calculaor Base is 7" x 7" ; rods 6" long. Set comes with 20 rods - 2 full sets of #0-9 Made in Spring Hill, Florida by CreativeCrafthouse