Some years  ago, there was a Mensa convention in San Francisco .  
Mensa, as you know, is a national organization for people who have an  IQ of 140 or higher.








Several of  the Mensa members went out for lunch at a local cafe.   When  they sat down, one of them discovered that their salt shaker contained  pepper, and their pepper shaker was full of salt.     How could they swap the contents of the two bottles woithout spilling  any, and using only the implements at hand?   Clearly   --  this was a job for Mensa minds.








The group  debated the problem and presented ideas and finally, came up with a  brilliant solution involving a napkin, a straw, and an empty  saucer.






They called  the waitress over, ready to dazzle here with their  solution.






"Ma'am," they  said, "we couldn't help but notice that the pepper shaker contains  salt and the salt shaker  --  "




But before  they could finish,..........

the waitress  interrupted.   "Oh  --  sorry about  that."


She leaned over the table, unscrewed the caps of  both bottles and switched them.








The was dead  silence at the Mensa table.