One example
Crude thought, crude drawing. Sort of following on the
notion that cars are horses.
(1) Automobiles from 1905 to 1935 were squared two-box designs.
(2) After 1935 the two-box got rounded into the fastback. This has returned in modern times as minivan/SUV forms.
(3) More recent development of two-box is the mouse. Pointy nose, high butt. Most small sedans in the last decade or so are mice.
(4) The three-box was always present as coupes, but reached its platonic perfection with the 1952 Ford. GM and Chrysler picked this up in 1955 and it continued through the 60s and 70s, until Chrysler's minivan pulled the norm back toward two-box.
(5) The three-box softened in a convex way. Platonic was the '53 Studie, returning later in less graceful form, eg Caddy Seville and Chevy Vega.
(6) BUT: Cars have never rounded CONCAVELY. Even the slightest suggestion of a swaybacked nag refuses to sell. I can think of EXACTLY ONE example of a swaybacked three-box.
Behold: The 1958 Studebaker.
High on BOTH ends, low in the middle. Every angle is perfectly wrong. Considering that this is a modified version of the platonic convex '53 with every angle perfectly right, it's quite a significant negative achievement.