The Poggendorff illusion is a distortion illusion in which
the two ends of a straight line passing behind a rectangle appear offset
when, in fact, they are aligned. It was discovered in 1860 by the physicist
J. C. Poggendorff, editor of Annalen der Physik und Chemie, after
receiving a letter from the astronomer Friedrich Zöllner.
In this letter, Zöllner described an illusion (see Zöllner
illusion) he had noticed on a fabric design in which parallel lines
intersected by a pattern of short diagonal lines appear to diverge.
- Gillam, B. "Geometrical Illusions." Scientific American,
242: 102-111 (Jan. 1980).
AND IMPOSSIBLE FIGURES