Source : Webster's Revised Unabridged Dictionary (1913)

Wheatstone's rods \Wheat"stone's rods\ (Acoustics)
   Flexible rods the period of vibration of which in two planes
   at right angles are in some exact ratio to one another. When
   one end of such a rod is fixed, the free end describes in
   vibrating the corresponding Lissajous figure. So called
   because devised by Sir Charles Wheatstone.