Canard-lapin retouché - A black and white drawing of a duck

"Kaninchen und Ente" ("Rabbit and Duck"), the earliest known version of the duck–rabbit illusion, from the 23 October 1892 issue of Fliegende Blätter (http://diglit.ub.uni-heidelberg.de/diglit/fb97/0147?sid=8af6d821538a1926abf44c9a95c40951&zoomlevel=2). It is captioned, "Welche Thiere gleichen einander am meisten?" ("Which animals are
most like each other?")