The key tool in this type of design was the divider, with which you could step out these ratios. And if you were going to reproduce a design, you just needed to know the "musical score," as there were no measured drawings: the width of the drawer is five times its height, the casing of the window is 1/6 the width, etc... The height of this form of design was the "Classical Orders," and studying them was a crucial way that artisans educated themselves. A bit like practicing the musical scales, drawing and redrawing Ionic columns and the like woke one's eye to these relationships and trained artisans in proper proportions.
Why did all of this end? As the Industrial Revolution erupted, machines took over production from artisans. Rather than tools being an extension of the maker, the maker became an extension of the machine. And machines don't deal in ratios; they need cold numbers. And so, measurement overtook proportions as the currency of design, and the "frozen music" of pre-industrial design was largely lost from made objects.
This has gotten me thinking about spoon design. What are the proportions that work best for eating spoons? What is the unit of measurement? For a while I messed around with length as the unit, with each part of the spoon taking up one third of the total: bowl, stem, handle. How long should an eating spoon be? Taking a cue from Walker and Tolpin, I used a body measurement: the span of my hand. (By the way, the metal soup spoons in my kitchen are about the span of a hand.) This worked OK, but really the crucial measurement of an eating spoon is not its length. It is the width of the bowl. If you are going to put the spoon in your mouth, it can only be so wide (I realize some eating spoons are made for "sipping" and are not supposed to fit in the mouth). Once you determine the ideal bowl width, all other elements of the spoon grow in proportion to that. You scale it down for the details, and scale it up for the overall dimensions.
I will add some drawings I have made when I can get near a scanner... More to come.