I've recently been interested in the study of metamathematics, as mathematical theories about mathematical theories has quite the charm of novelty to it from the perspective of an undergrad. I recall in an interview with Steven Wolfram that some regard prominent figures (like Bertrand Russel) to have done extremely esoteric research in even higher 'orders' of metamathematics. I.e; meta-mathematics and etc.
Although there may not be a method to measure such, what is the highest order of metamathematics that is has been reached, or is being researched in academia?
Any insight or references to papers would be appreciated.