There are a several guides or systems, that are said to help one learn to “design” furniture. The most cited examples are, the column orders, the golden rectangle and the Fibonacci series among others. There are problems with all of the systems one is that they were not developed to help design anything. They were used after the fact to help analyze a piece that had already been designed and built, in that regard they can be helpful.
While there must be pieces somewhere that were built using one of these systems, the vast majority do not fit. All you have to do is try to apply any of the systems to a piece, very few if any pieces will fit exactly into one of the systems. You would think that if the designers of the pieces we believe to be noteworthy had used a system up front that there would be pieces that fit the system precisely. While there are pieces that have some elements that fit a system and others that come close, it is rare to find an antique piece that fits a system exactly. Throughout history many talented individuals with a natural sense of design built furniture, much of it following the fashion of the day, and at a later date, people tried to figure out how they did it.
Another problem with any system is that how we see any piece is modified by the place in which it is seen. In other words how we see any piece depends on where we see it. A seven foot tall piece may look too tall in a room with eight foot ceilings and too short in a room with twelve foot ceilings. Just as a shirt with horizontal stripes will make you look heavier than a shirt with vertical stripes. Design is dependent on how we see and none of the systems acknowledge this.
In the twentieth century science began to understand how we see and how it influences design. If you want to learn to design furniture you need to study the modern understanding of vision and it’s connection with design. There are hundreds of books on design many good and many bad, studying design is not easy, that’s why so many people search for and advocate some simple system.