The truth is, the science of Nature has already been too long made only a work of the brain and the fancy. It is now high time that it should return to the plainness and soundness of observations on material and obvious things.
The True Theory of Elasticity or Springiness (1676)
Anagram to establish priority in the discovery: revealed in De potentia Restitutiva (1679) as
UT TENSIO, SIC UIS
(as is the extension, so is the force)