The Republic by Plato Part 3 Page 95

Therefore, as I was just now saying, we must enquire who are the best guardians of their own conviction that what they think the interest of the State is to be the rule of their lives. We must watch them from their youth upwards, and make them perform actions in which they are most likely to forget or to be deceived, and he who remembers and is not deceived is to be selected, and he who fails in the trial is to be rejected.

That will be the way?

Yes.

And there should also be toils and pains and conflicts prescribed for them, in which they will be made to give further proof of the same qualities.

Very right, he replied.

And then, I said, we must try them with enchantments — that is the third sort of test —