This device can show that the pressure of liquids depends on the depth and not on the shape of the vessel. The two drawings showing similar devices made by Max Kohl and E.Leybold Nachfolger are useful in order to understand the operation of the device. It was accompanied by a set of 4 vessels of different shapes which are missing together with a balance and a balance pan.
The following text is from E.Leybold Nachfolger catalogue.
"The cylindrical vessel is first screwed on, 100gr put on the scale pan and water poured into the vessel. If more than a few drops of water flow out the point of support of the balance beam is raised or lowered, by turning the two screws until the aperture is sufficiently closed. The 100gr are now removed and the water allowed to flow away. The vessel, the metal band and the bottom plate are now dried carefully with filter paper; a beaker is moistened, tarred and 80gr of water weighed out therein. The 80gr weight is now placed in the balance pan and the weighted quantity of water poured into the glass cylinder without touching it, as shaking easily displaces the bottom plate. With careful manipulation no water runs out. Now mark the position of the water by means of the movable pointer and pour in some more water; water then flows out until the level indicated by the pointer is re-established. The other glass vessels are screwed on and it is seen that in one case more, in the other case less water than 80gr are necessary to cause the water to discharge, but the same height of water is in each case required."