Thomas Edison had a unique way of hiring engineers. He'd give the applicant a light bulb and ask, "How much water will it hold?"
There were two ways to find the answer. The first choice was to use gauges to measure all the angles of the bulb. Then with the measurements in hand, the engineer would calculate the surface area. This approach could take as long as twenty minutes.
The second choice was to fill the bulb with water and then pour the contents into a measuring cup. Total elapsed time: about a minute.
Engineers who took the first route, and performed their measurements by book, were thanked politely for their time and sent on their way. If you took the second route, you heard Edison say, "You're hired."
(From Managing By Storying Around, by David Armstrong)
The Manager's Intelligence Report