Just a few days ago I was reading "Thinking with demons," an excellent history of ideas about witchcraft in Europe, and was struck by the following passage about a 16th century drawing of three witches by Hans Baldung Grien:

Informing everything in the scene, and establishing iconographically that it is indeed a scene of witchcraft, is the gesture of the witch who, bent on one knee, stares backwards at the world through her own legs. According to a contemporary German proverb those who adopted the pose would be sure to catch sight of the devil. This is perhaps the reason why the motif is also found among the monsters and devils who populate two widely separated versions of that most demonological of picture subjects, the temptation of St Anthony—those of Hieronymus Bosch (c. 1490s) and Jacques Callot (1635).

So it was fascinating to learn from this news article that "There are also regions of Japan where the folklore says that one can see ghosts, the world of spirits and demons, or the future by looking upside down through one’s legs."