What weird or unusual superstition or old wives tales do you know?

I saw something today about superstitions and I figured that it would be fun to hear of some unusual superstitions/old wives tales from different lands.
Please say what country or nationality the superstition comes from.
I remember in Japan, we were told not to leave chop sticks sticking out of your bowl. It was suppose to bring bad luck to the restaurant. Don’t remember the reason behind it though.
Growing up in the United States, you don’t step on a street crack or your break your mothers back.
Growing up in a Puerto Rican household (although I do not know if this is solely a Puerto Rican superstition) you don’t sweep over your feet or you’ll never get married.
This is just for fun. I hope to hear some interesting superstitions. If you know the history behind any of them, I would be glad to hear them.