As we all know, 100% universal franchise is fiction - in every country, no matter how democratic, SOME people are excluded from franchise (felons, under-18-year-olds, foreign nationals, etc...).
Was there ever a political jurisdiction that restricted franchise very explicitly by intelligence threshold (e.g., you can vote at 13, if you're smart enough, but you can't vote at 30 if you're not smart enough to be trusted to vote).
 - I am clearly excluding cases where the electorate themselves are naturally IQ clustered, such as academia elections. Just general, at-large governance elections are in scope.
 - Intelligence as measured reasonably directly - e.g. while someone may (correctly or not) claim that a poll tax is correlated to a degree with intelligence, the example is out of scope for the question, unless the organizers explicitly proved that their proxy test both highly correlates with intelligence, AND upfront-explained it this way. FWIW, usually poll taxes are explain in ways unrelated to intelligece
 - Issues such as whether IQ or some other measure to verify intelligence work or not; or if they are "fair" or not, is outside the scope.