https://www.smithsonianmag.com/history/charles-proteus-steinmetz-the-wizard-of-schenectady-51912022/Henry Ford once balked at paying $10,000 to General Electric for work done troubleshooting a generator, and asked for an itemized bill. The engineer who performed the work, Charles Steinmetz, sent this: "Making chalk mark on generator, $1. Knowing where to make mark, $9,999." Ford paid the bill.
Ford, whose electrical engineers couldn’t solve some problems they were having with a gigantic generator, called Steinmetz in to the plant. Upon arriving, Steinmetz rejected all assistance and asked only for a notebook, pencil and cot. According to Scott, Steinmetz listened to the generator and scribbled computations on the notepad for two straight days and nights. On the second night, he asked for a ladder, climbed up the generator and made a chalk mark on its side. Then he told Ford’s skeptical engineers to remove a plate at the mark and replace sixteen windings from the field coil. They did, and the generator performed to perfection.