There was a Mensa convention in San Francisco.
Mensa, as you probably 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 café.
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 without 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 her with their solution.
“Ma’am,” they said, “we couldn’t help but notice that the pepper shaker contains salt and the salt shaker has pepper.”
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.
There was dead silence at the Mensa table.