From one of the comments:<p><i>I worked in one of these large rooms with 60 or 70 drawing boards in 1958 through 1965. In those years, besides paper, we utilized Vellum which is a stiffened cloth type medium. Not only could paper drawings be edited, but some were inked. The inked ones were harder to erase and change but they made much clearer blueprints.</i><p><i>In those years we had only one 100 key calculator for the entire office. You could add, subtract, and multiply; division was more difficult and square root was the most difficult. We also shared one letter size copier which utilized a "wet" system developer. after copying, the pages were hung to dry. Oh, what a change when each of us could have a personal hand held calculator. We didn't even have the more modern drafting machines but our tables had a "constant" horizontal as in some of the photos. To assess the square feet in asymmetrical or unusual land boundary shapes we used a "planimeter" that was nicknamed a "buggy" and traced the boundaries of the 2D drawing. I think lots of things are changed particularly now that I'm 80 years old.</i>