As with the chest, bench, and table patterns, I took it as a challenge to make the most of a sheet of plywood.
This is a pattern for 2 Savonarola-style camp chairs that I drew up. For a more authentic version, made from boards instead of plywood, please look at this pattern. My design was inspired by theirs.
I am still looking for a 14th Century version of this chair. Most of the surviving examples seem to be from the 15th Century. One very interesting picture is this detail of "Saint Martin Renouncing the Sword" by the 14th Century Italian painter, Simone Martini (1283-1344). The nobleman's seat is a sling-seated version of the X chair, but turned sideways so that the X is on the side, not the front.