Literacy Tests for Voters
J. S. Mill argued that voters should have to satisfy general literacy and numeracy tests before being allowed the franchise. The idea doesn't sound ridiculous in the abstract, but the danger lies in how the tests are administered.
This is apparently the kind of literacy test used to deprive blacks of the vote in the US South. It's full of trick questions (like 25) and others that are so ambiguous (20 and 27) as to, in effect, allow the sheriff arbitrary power to decide who has the answers right and wrong.