Digital Companion to C. S. Peirce
1908-12-24 | Letters to Lady Welby | CP 8.347
…Signs, in respect to their Modes of possible Presentation, are divisible […] into
A. Potisigns, or Objects which are signs so far as they are merely possible, but felt to be positively possible; as, for example, the seventh ray that passes through the three intersections of opposite sides of Pascal’s hexagram.
Link to image of Pascal's hexagram in Wikipedia, suggested by Brian Josephson