When I began my career I found it interesting to figure out where the numbers appearing in electrical power distribution "cookbook" tables came from.
One set of tables that fascinated me was that used for implementing MIL STD 414, specifically as used for sample meter testing.
Another set of tables was that used to calculate fault currents and voltage drops on distribution feeders.
I was amused to find a SINGLE ambient temperature (around 68°F) used in the tables, making computations quite lacking when used to determine how much current could be carried in the middle of winter (30° might be more practical) or in the middle of summer (90°F might be more practical) -- both times with high electricity usage.
I automated both functions and discovered that the government MIL STD 404 tables contained errors. Alas, as my employer was under the mandate to "use those particular tables" we were forced to continue ... errors and all.
It was also this same time period when I found it most like a puzzle to construct nomograms that could be used to perform the calculations needed on a daily basis. Nomograms have been made obsolete by personal computers, but they were still a lot of fun to construct.