A bunsen burner
A Bunsen burner was a small device used to heat liquids with a flame.
The Akaali Apothecary Riaan had such a device in her shop and instructed "Jon" to turn down the flame as she was preparing tea. (ENT: "Civilization")
The props requirements section of the call sheet listed a "Bunsen burner" in these scenes.
In 2367, one of USS Enterprise-D's classrooms had several Bunsen burners on a table. (TNG: "Reunion")