Accused witches were said to have used a ligature, a knotted loop of thread, to induce various marital problems, including barreness in women and impotence and even castration in men.
Fear of the ligature was very widespread in 16th century France and most couples of Languedoc chose to marry privately to avoid the curse that would be customarily thrown during the sacrament of marriage. It was believed that when the priest blessed the new union, the witch slipped behind the husband, knotted a thread and threw a coin on the ground while encanting the Devil. If the coin disappeared, that is, if it was taken by the Devil, the newlyweds were destined for a bad marriage.
The curse could be undone by untying the knot.