...If one places the points of a compass more than one centimeter apart on the nape of an experimental subject's neck, the subject can clearly distinguish between the two points (Figure). Each point is located at another place. If one moves the points down toward the back without changing the distance between them, they get closer and closer in the tactile space of the experimental subject until they seem to be at the same place. : https://germanhistory-intersections.org/en/knowledge-and-education/ghis:document-143
