by Tesla when he worked for Waltham Watch company
Speed Indicator - 1918 August 6 - Speedometer that possesses the feature of: Linearly proportional torque readings; Strong low speed torsional effects; not affected by atmospheric density, temperature, nor magnetic influences; Rugged; Simple; Economical.
"A new type of speed measurement instument wherein the adhesion and viscosity of a gaseous medium, preferably air, is utilized for torque-transmission from a primary driving to a secondary pivoted and torsionally restrained member under conditions such that the rotary effort exerted upon the latter is linearly proportional to the rate of rotation of the former."
To give an example of an earlier work of his, a "air-drag" speedometer... to illustrate the mental ability of this genius when he is only describing a speedometer for pete's sake!
So, in nearly every vehicle I've ever admired lie the evolved forms of two things that Nicola Tesla invented.... radio and speedometers, which you will see dozens of photos of each here in this blog because I dig the variety in design of both of them. I hope you enjoy!
I just learned of this myself, though I've admired Tesla for some time due to other things he invented and accomplished (truely a unique and remarkable man who invented things other genius' could not even comprehend) by reading the last page of the March issue of Automobile magazine
http://www.automobilemag.com/index.html
The above was first published in the Nov 1955 Hot Rod, but I don't have that one, and instead found it in the 25th anniversary issue of Hot Rod
Above image, and for more info go to: http://chopcult.com/news/blogs/von-dutch-monday-xiii12-21-09-22-06-02.html
For all the bio on the inventor, his difficulty working out how to make the train stay upright through curves, and more. Good reading. 
