As a source, the following can be used:

• a hollow cube of copper plate, the vertical walls of which are covered with different substances, which is filled with water and heated to 100°C to make it boil by means of an alcohol burner placed in the hollow part of the support (Leslie's cube);
• a copper plate heated to about 400°C;
• a platinum spiral heated to incandescence;
• a Locatelli lamp (which bears the words: R. Menilmontant 26 - Lampe Locatelli);.
• miscellaneousous accessories can be mounted on the rule by means of special supports. i.