I ordered some cloth menstrual pads from saucytots.com. When they came, there was a free gift in the package - a couple of gumdrop shaped things made of wax. I asked the owner what these were and she said they were "wax tarts" and you melt them in a "wax tart burner" to release fragrance. (The scent I got was called "Candy Cane.")
Google turns up loads of these wax tart things. I never knew.
The disturbing part is that many of the web sites featuring these wax tarts use "fragrance" as a transitive verb. "With our wax tarts, in your tart melter, you can fragrance a very large area for many, many hours before changing your tarts."