My brother just gave me a cup carved from wood from the Quassia tree. He bought it in Suriname, South America. It looks a bit like this. A simple cup made from unpainted, untreated light colored wood.
When you put water in the cup, the water becomes very bitter tasting in seconds. That is because the wood contains (less then one percent of quasin, the most bitter tasting chemical found in nature.. The wood also contains many other known and unknown chemical compounds, many used as traditional medicins and insecticides. it was well known in the 19th century, but I had never heard from it in modern times. Quassin is also the stuff used in the nail polish used to teach little kids not to suck their thumbs or bite their nails.
In Suriname, apparently many people take one cup of quassi water a day for health reasons.The taste is even added to soft drinks because people have grown to like the taste, much like quinine has been added to tonic soda water.
The weirdest thing is how unending the cup is. You can pour water in it and drink it for years, keep it unused for years, and if you use it then after years it will still turn the water in it bitter in in instant.