Buried around 1800, 1875 this mans casket was discovered near a train station in Philadelphia. Radiography has shown that the earliest date of death is 1824. Now resting at the Smithsonian museum, his body was displayed from 1970s-1991. Soap-Man was found with a Soap-Lady, who now rests at Mutter Museum in Philadelphia.
Mummification
The man turned to mummy due to a leak in his casket; alkaline water from from the soil combined with the persons body fat mummified the remains.
References
http://earthsky.org/human-world/soapman-man-buried-in-1800s-has-turned-to-soap
https://bonesdontlie.wordpress.com/2011/01/16/the-soap-man-and-lady-revisited/