Tait was very interested in classifying knots. He hoped to use them as models of the atom, but of course this was wrong: he knew nothing of electrons or quarks, still less of photons or gluons or gravitons. However string theory has revived interest in knots: the Jones polynomial for the left handed trefoil is
t+t^3-t^4.

A trefoil the simplest nontrivial knot. It is chiral; ours* is left handed. As you can see it is tricolourable. Resources about knots can be found here.

* Picture created by Jim Belk.