While spirit photography, which claims to capture ghosts on film, dates back to the middle of the 19th century—William H. Mumler was tried in New York for faking photographs in 1869—the practice has had tremendous longevity. These photos, taken in the first couple of decades of the 20th century, were part of a resurgence of interest in “psychic photography” after the tremendous losses of World War I.The “mediums” credited with some of these photographs, Scottish brothers Craig and George Falconer, incorporated the process of making a photograph into their show. The Falconers would invite audiences to watch them load film into their cameras and produce prints, “proving” that no trickery was afoot.

Read More: Spirit photography: Craig and George Falconer images of ghosts.