Until very recently, the miracle proportion of modern design followed the quest in fulfilling the Golden Ratio. Most designers take severe steps to mathemagic their designs to meet the natural relation that has been mathematically expressed as 1:1.618, or the Greek letter Phi. This relation has been identified and experimented upon since around 300 BCE. Euclid is credited with first describing the proportion mathematically. Fibonacci didn’t invent the sequence that bears his name, just related it in publishing Liber Abaci in 1202 CE. By that point, the whole number relations had been known and used to approximate Phi for at least a millennium and a half. We know this not only by the books on design have have survived, but also by determining the relative proportions of extant pieces of material culture. Granted, some of those objects have been incorrectly attributed to contain relations perfect to Phi, but that is a matter of faux-intelligencia conceit.
The decimal expression of this relation didn’t exist until 1597 CE, attributed to Michael Maestlin in a letter to his student Johannes Kepler. But wait, we’re talking artistic design, not astronomy, right?
Exactly. The decimal expression didn’t become “common” knowledge until the 17th century, around the same time that a hybrid of existing carrot species’ resulted in the cultivation of an orange colored carrot. That is more than four centuries after Liber Abaci, and more than twenty centuries after Euclid published the formula to determine the number.
The point being it is unsuitable to attempt to design medieval and renaissance furniture using that decimal expression. This is especially important to remember when recreating specific period designs or themes. There are more than a few examples that don’t follow a proportion along the “Golden Ratio.” If the designers of that age didn’t use the decimal proportion, or didn’t even use any one proportion uniformly, then why should any modern reproductionist?
That is not to say that the common proportions are not closely related to the decimal expression, but it is incorrect to use an artificial and “modern” expression when the historically correct ones are so handy. Vitruvius’ Ten Books of Architecture are publicly available, and a good reading will demystify the majority of the relations to use in Renaissance Design, and early Medieval as well.
After all, Fibonacci never ate an orange carrot, so why should you?