Among America’s oddest purveyors of the unknown was William Mumler who was purported to take photographs of the dead, Marc Hartzman, author of "American Sideshow", told C2C on 8/24/15. Pictured left to right: Moses A. Dow with the "ghost" of his assistant, Mary Todd Lincoln with the "ghost" of her husband, and the medium Master Herrod with a single "ghost." More on Mumler here.