Just out of high school I was visiting some folks in the Amazon basin who did oilfield support work. (Long story.) They were talking about some building modest but non-trivial piece of engineering, like a big tank. One of them, a grizzled old guy who looked more like a motorcycle gang leader than an engineer, talked through the problem in just the way you describe, doing estimates of dimensions, weight, support structure, materials needed, and the like. No calculator, no paper, nothing but what he had in his head from years of experience.<p>I had assumed that kind of work was done very formally, with equations and blueprints and the like. It blew me away to see somebody do something so familiarly, and I&#x27;m sure he was spot on. It definitely inspired me when I went to college.