In the 1975 New Columbia Encyclopedia you’ll find a biography of Lillian Virginia Mountweazel (1942-1973), an American fountain designer and photographer best known for Flags Up!, a collection of photos of rural mailboxes.
Mountweazel never existed. She’s an example of a nihilartikel, a deliberately fake entry in a reference work. They’re used to catch copyright infringers. For the same reason, telephone directories include fake entries, and maps sometimes include nonexistent features.
It must be fun writing these. According to the New Columbia article, Lillian Mountweazel died in an explosion while on assignment for Combustibles magazine.