In the 1948 reprint/edit of his 1930 novel Skylark Three, E. E. Smith postulated a series of 'subelectrons of the first and second type' with the latter being fundamental particles that were associated with the gravitation force.
Preon |
Preon and models inspired by preons such as the Ribbon model of Standard Model particles by Sundance Bilson-Thompson, based in braid theory and compatible with loop quantum gravity and similar theories.