The capillary tube that ends below in a bulb containing mercury is connected to a test-tube on one side that contains a roll of paper on which are handwritten several temperatures on the Réaumur scale between − 45° and + 80°. It reads:  0° ice, 80° boiling water, which are the fixed points on the Réaumur temperature scale.
On the paper is also written the name of physicist Angelo Bellani (1776-1845), founder of the firm bearing his name that makes mercury thermometers.

Device on display.