Hydraulic weighing scale
Stand on the designated point. Observe the level of the liquid in the tube. The height of the liquid column should correspond to your weight measured in kilograms.
How does it work
The tube filled with liquid is connected to the platform that you stand on. By pushing the platform down, accordingly to the Pascal’s law, you increase the pressure inside the whole tube. This pressure, called the hydrostatic pressure, depends on the fluid density, gravitational acceleration, and the height of the liquid column. Neither the density, nor the gravitational acceleration changes during the experiment, so the only effect of the pressure increasing is the liquid level going up.
The French scientist, Blaise Pascal, performed an experiment in which he put a long vertical tube into a leakproof wooden barrel, filled with water. Small amount of water poured into the tube made the barrel burst. The experiment proved that the pressure inside the container depends directly not on the weight of the liquid column but on its height.