After his divorce with Mileva, Einstein published a paper in Nature entitled "The Theory of the Affine Field." Allegedly it confused renowned scientists. Why? What did the paper accomplish? What was it about, really?
It was Einstein's reaction to Eddington's ideas about a unified field theory based on a symmetric affine connection. Ultimately, it did not go anywhere.
Cf. Hubert F. M. Goenner: On the History of Unified Field Theories. There's also a second part.