To make soap, you must mix grease or fat with lye or some other alkaline substance. Sometimes, however, the stuff makes itself. If, for example, water laced with alkaline soil seeps into a coffin, it can transform a human body into soap. (This cadaver soap is known as grave wax or adipocere.) Here’s a picture of a “soapman” in the collection of National Museum of Natural History in Washington, just posted in the Smithsonian’s “Snapshot Series.” It belongs to a man who was buried in Philadelphia around 1800. His body was discovered in 1875 during an excavation to build a train depot. This particular example of grave wax is kept under lock and key in the museum’s “Dry Environment room,” so this is the closest you’ll get to seeing it. But if you want to see grave wax in person, be sure to get to the Mutter Museum in Philadelphia, which keeps its eerie “Soap Lady” under glass.