h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

My father will never give you the saltpot in the hand.He always puts it down first.He says its an old tradition dating back to Roman times when the soldiers were paid in salt and so, giving salt into the hand is the same as giving away money.

I've just re-read the article, including the bit about throwing salt over your left shoulder. I always understood that you throw salt over your left shoulder to blind the devil that sits there, not to knock him off. That way, he can't see the "sin" you've committed by spilling salt. Salt which used to be a very expensive commodity, and therefore was not to be spilt! One of the reasons Roman soldiers received part of their pay in salt was because it was so valuable. In fact, if a commander felt that one of his men had not performed up to standard, he would withold some of the salt!