The sealed envelope test; a double blind experiment.

The sealed envelope test was applied to both Leonora Piper and W. Stainton Moses. Information was sealed in envelopes that neither had any knowledge of, nor access to, and they would then talk to the spirit world to obtain the messages

The Muse of Automatic Writing

Hélène Smith (real name Catherine-Elise Muller, 1861, Martigny (the capital of the French-speaking district of Martigny in the canton of Valais in Switzerland.)― 1929 Geneva) was a famous late-19th century French psychic. She was known as "the Muse of Automatic Writing" by the Surrealists, who viewed Smith as evidence of the power of the surreal, and a symbol of surrealist knowledge. Late in life, Smith claimed to communicate with Martians, and to be a reincarnation of a Hindu princess and Marie Antoinette.

Automatic writing in "Martian" produced by Smith at a séance

Cryptamnesia

Théodore Flournoy (1854 –1920) was a professor of psychology at the University of Geneva and author of books on spiritism and psychic phenomena.

Interested in philosophy and religion, Théodore Flournoy spent time in Germany to familiarize himself with the philosophy of Immanuel Kant, whose work he later taught at the university. After becoming a medical doctor, he was appointed a professor of physiological psychology at the University of Geneva in 1891.

His studies of the medium Hélène Smith were turned into a book, Des Indesà la planète Mars, which caused a considerable sensation in psychological and parapsychological circles in Europe and the United States. In it he described the phenomenon of "cryptamnesia," forgotten memories that reappear without being recognized by the subject, who believes they are new.