Shop drawing, side elevation of the Barcelona stool, office of Mies van der Rohe. Sorry about the distortion lower left on the image, it was very hard to shoot this flat.
It’s a rather interesting drawing, and in one respect absolutely baffling — it’s generating its curve geometry from radius marks that have their center point simply out in space, if you will, their location not defined. So anyone actually fabricating this working off of the numeric instructions wouldn’t actually be able to generate the curves as there is no fixed location where the curves are centered.
Other aspects of the geometry are defined, like the width of the top elements, the width of the feet, the height of the assembly (a dimension out of the image to the left) and the degrees angles defining the arms leaving the center crossing. Otherwise, the curve itself is not being controlled.
Still, the geometric pattern of all these control lines is kind of hypnotizing.