Tonka beans are the seeds from the fruit of the Dipteryx odorata tree in the South American rainforest. They have a deep vanilla-like scent from the high coumarin content they contain. The scent improves with age, and these have been stored for at least ten years.
In my book The Spirit of Botany, I include a recipe using a coffee grinder to turn them into a material to blend with herbs and resins as a charcoal-burning incense. I have worked with them in other ways as well, from tincture to oil infusion to sachet blends. They're also a very special offering to keep on personal altars.