TBH, familiarizing oneself with several subfields of a single field is still not very polymath-y though. Of course, all fields are just much bigger than they we

TBH, familiarizing oneself with several subfields of a single field is still not very polymath-y though. Of course, all fields are just much bigger than they were in the 15th or 18th century, so this is more difficult if you want to be actually useful, but IMO being a real polymath still entails being knowledgeable of various disjoint subjects. Like poetry, marine biology, and systems programming. And, of course, since software has been eating the world, domain knowledge about the field in which your software is actually used is one of the most valuable traits to have, because it matters very little how perfect and elegant your solution is if it is a solution to the wrong problem.