Konstantin Tsiolkovsky blower. The centrifugal fan is driven by a weight. The model is placed on a sort of boat whose recoil in a water tank drive a flexible needle, the needle indicating therefore the value of the aerodynamic drag.
<a href="//commons.wikimedia.org/wiki/User:Bernard_de_Go_Mars" title="User:Bernard de Go Mars">Bernard de Go Mars</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>