I found the following story on @HistoryWeird's blog here. The original source was Dr Mary Wood-Allen's What a Young Woman Ought to Know, London, 1889.
"Mary Wood-Allen (1841-1908) was an American physician, paediatrician and temperance advocate. Like many others of her generation Wood-Allen was a social purist, obsessed with the promotion of cleanliness, morality and wholesome thoughts. By the 1890s Wood-Allen was a public speaker in high demand and a prolific author of guidebooks on adolescence. Her message was strident and consistent: children must be protected from premature development, precocious sexual thoughts or activity and, above all, masturbation. In her 1889 book What a Young Woman Ought to Know, Wood-Allen walked young girls through life from puberty to marriage, outlining the ‘cans’ and ‘cannots’ of these formative years. Reading novels, for example, was a strict ‘no no’:
'"It is not only that novel-reading engenders false and unreal ideas of life, but the descriptions of love-scenes, of thrilling, romantic episodes, find an echo in the girl’s physical system and tend to create an abnormal excitement of her organs of sex, which she recognizes only as a pleasurable mental emotion, with no comprehension of the physical origin or the evil effects. Romance-reading by young girls will, by this excitement of the bodily organs, tend to create their premature development, and the child becomes physically a woman months, or even years, before she should."
'Another forbidden act was the seemingly benign habit of standing on one foot. According to Wood-Allen, continually favouring one foot could lead to uterine displacement, menstrual difficulties and constipation. And constipation itself exerted pressure on sexual organs, something 'known to incite self abuse':
'"…The common habit of standing on one foot is productive of marked deformities of both face and body and of serious displacements of internal organs… Standing continually with the weight on the left foot is more injurious than bearing it on the right foot, for it causes the uterus and ovaries to press upon the rectum and so produces a mechanical constipation, especially during menstruation."'