In 1929, Harry Palmer of Palmer Motor Co. in Boston, MA, made an experimental, air-cooled, four-cylinder, radial engine that gave 80 HP.

From Appendix 6: H.A. Palmer of Boston made this engine that looks toroidal and claims not to have connecting rods, camshaft, springs, and most of the usual classic engine parts.

"Palmer with his engine" (PiP = ps)