This is one of the most famous ghost photos of all time. It supposedly shows the "Brown Lady" who haunts Raynham Hall in Norfolk, England.

The image was taken by Captain Provand and Indre Shira (a pseudonym), two photographers on assignment for Country Life magazine. According to their later testimony, the pair saw an ethereal form descending the staircase and quickly snapped a picture.

Skeptics argue that the photo does not show a ghost, but rather was the result of mundane causes such as camera vibration, afternoon light from the window above the stairs catching the lens of the camera, and double exposure. What is not known is whether these effects were produced purposefully, or if they were the accidental result of a faulty camera.

David Starr Jordan, president of Stanford University, published an article in Popular Science Monthly describing the discovery of a new form of photography that he called Sympsychography. Starr explained that it allowed invisible brain waves to be made visible on a photographic plate -- similar to the way in which invisible X rays produce an image on a photographic plate.

The first test of sympsychography, Starr wrote, had been conducted by Cameron Lee, who burned an image of a cat onto a photographic plate merely by thinking of a cat. The Astral Camera Club, which met on April 1, then took the concept one step further. Seven of its members simultaneously concentrated their minds on a photographic plate while thinking of a cat. What emerged was not one man's image of a cat, but rather a joint "impression of ultimate feline reality." The resulting picture (shown here) was reproduced in the article.

Starr wrote, "it will be noticed that this picture is unmistakably one of a cat. But it is a cat in its real essence, the type cat as distinguished from human impressions of individual cats."

Jordan thought the readers of Popular Science Monthly would immediately recognize his article as a joke. Instead he received numerous letters from people who had taken the article at face value. One clergyman even confided to Starr that he had prepared six sermons on "the Lesson of the Sympsychograph."