I was about three or four and in a group music lesson. We were taking a five minute break and another kid caught me in the corner picking my nose and sampling the contents. Between her 'EWWW!!!' (she was about nine - I was the youngest kid there by a good four years) and her inevitable tattling on me to the teacher and all the other kids, I was able to convince her that my family came from Russia and in my family (and all over Russia, presumably) it was a ritual we did for good luck.