Napier's bone

 NAPIER'S BONE:

•        Napier's Bone was invented by John Napier who was a Scottish mathematician.

•         It is a device consisting of 10 rods engraved with numbered parts. Each rod was further divided into 9 diagonal number parts.

•          The purpose of Napier's Bone is to extract square roots, divisions, multiplications.

  
  source: pinterest.com

•         The features of Napier's Bone are as follows:  

        a) It helps in rapid calculations,

        b) It is a small device of calculation.

        c) Usually it is made of wood.

source:wikipedia.org