the world > the supernatural > the occult > spiritualism > [noun] > spirit-writing > message (3)
Chiefly Spiritualism. A photographic or photograph-like image attributed to a supernatural or spiritualistic cause. Now rare.
Spiritualism. A message supposed to have been written by a spirit, or by psychical means; a spirit writing. Now rare.
Spiritualism. A piece of automatic writing (automatic, adj. 5a). Also figurative. Now rare.