"...with mathematic precision" - continued...

With this transition to the science of fatigue, however, physiology does remain loyal to its instruments of objectivity, including the dynamometer, which at that point and after several modifications has come to be known as an ergograph. It was developed in 1884 by Angelo Mosso, a physiologist from Turin, Italy, and consists of two parts: a positioning apparatus, with a supporting plate for the arm and metal tubes which keep the index and ring finger still, as well as a recording device with a metal pin and goose quill that moves via a tension wire with leather band, weight and pulley (Mosso 1891, pp. 104, 107 ff.).

Ergograph according to Mosso (Caspari 1911)

The strength of the middle finger is measured as the subject moves his finger, either on his own at a given tempo, supplied by a metronome, or as the finger contracts in response to electric stimuli.