I don't know what's the correct super-smartness cluster, so I cannot make objective predictive definition, at least yet. There's no need to suffer from physics envy here - a lot of useful knowledge has this kind of vagueness. Nobody managed to define "pornography" yet, and it's far easier concept than "super-smartness". This kind of speculation might end up with something useful with some luck (or not).

Even defining by example would be difficult. My canonical examples would be Feynman and Einstein - they seem far smarter than the "normally smart" people.

Let's say I collected a sufficiently large sample of "people who seem super-smart", got as accurate information about them as possible, and did a proper comparison between them and background of normally smart people (it's pretty easy to get good data on those, even by generic proxies like education - so I'm least worried about that) in a way that would be robust against even large number of data errors. That's about the best I can think of.

Unfortunately it will be of no use as my sample will be not random super-smart people but those super-smart people who are also sufficiently famous for me to know about them and be aware of their super-smartness. This isn't what I want to measure at all. And I cannot think of any reasonable way to separate these.

So the project is most likely doomed. It was interesting to think about this anyway.