http://www.nature.com/nature/journal/v427/n6972/full/427297a... How one intuitive physicist rescued a team from fruitless research.

Quote from Freeman Dyson:

In desperation I asked Fermi whether he was not impressed by the agreement between our calculated numbers and his measured numbers. He replied, “How many arbitrary parameters did you use for your calculations?” I thought for a moment about our cut-off procedures and said, “Four.” He said, “I remember my friend Johnny von Neumann used to say, with four parameters I can fit an elephant, and with five I can make him wiggle his trunk.