John D. Rockefeller

Forty drops of solder. That was how much metal went into sealing each kerosene can. To most visitors, it might have seemed too small a detail to notice.

During a visit to a Standard Oil canning plant in New York in the early 1870s, John D. Rockefeller watched the work and asked how many drops were being used. The answer made him wonder: could the same job be done with less?

The cans carried kerosene, a fuel for lamps, to distant customers. Their seals had to hold. Saving solder would be no improvement if the oil leaked out along the way.

Rockefeller asked the workers to try thirty-eight drops. They tested it. Some cans leaked.

Then they tried thirty-nine. The cans held.

One drop. It was almost nothing to look at, but Standard Oil sealed enormous numbers of cans. That tiny saving, repeated again and again, became a substantial reduction in cost.

Rockefeller had asked the question; the workers' tests found the answer. Thirty-eight used too little. Forty used more than the job required. Thirty-nine preserved the seal and removed the waste.

In the portrait, his finger draws our attention to that small ring of solder. The ledger beside it points to the larger idea: a detail worth pennies can matter enormously when you do it thousands of times.