Zener Cards: The original name given to the ESP cards; named after the perceptual psychologist Karl Zener, a colleague of Rhineās, who apparently suggested the symbols to be used on the cards (circle, cross, square, star, and wavy lines).
References
- Parapsychology by Michael A. Thalbourne, Republished by Puente Publications, Charlottesville, VA, USA, 2003