This 19th-Century 'Toy Book' Used Science to Prove That Ghosts Were Simply an Illusion

If a reader stared at one of Spectropia’s illustrations under a strong light source for about 20 seconds and then gazed at a blank wall in a darkened room, a version of that image in inverted colors appeared. Phillips Library, Peabody Essex Museum In 1864, a book called Spectropia set out to expose how the brain can trick people into believing they’ve seen a ghost. Across 27 pages, author J.H. Brown laid out how…