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

According to Mosso's experimental setting the only thing missing in his preceding figure is the flame-blackened rotating cylinder, called a "kymograph" or "wave recorder":

Kymograph for measuring blood pressure according to Ludwig, 1847 (left) and
Blackening equipment including gas burner and the blackening nozzle by Jaquet (right)

Thus, an individual fatigue curve could be drawn on the slowly rotating cylinder. The char layer was fixed with a layer of shellac after the recording had been taken.