The Collaborative International Dictionary of English v.0.48:

Napier's bones \Na"pi*er's bones`\, Napier's rods \Na"pi*er's
rods`\
   A set of rods, made of bone or other material, each divided
   into nine spaces, and containing the numbers of a column of
   the multiplication table; -- a contrivance of Baron Napier,
   the inventor of logarithms, for facilitating the operations
   of multiplication and division.
   [1913 Webster]