Can a proverb include, within few words, traces of great historical transitions? This is the question that is at the basis of this contribution whose intent is to reconstruct, through the analysis of the proverb An illiterate king is a crowned ass, the main circumstances that, from the classical era to the early stages of modernity, and through the Middle Ages, have characterized the various ways of understanding the education of the king and the relationship between culture and political power. Starting from the medieval origins of the proverb, I first took a step back in time in order to look at the semantic development of the word litteratus compared with classical texts; then a step forward, to examine the differences due to the transitions to Humanism. In this way a wider framework, that made clear the evolution in time of an issue with strong political and cultural repercussions such as the education of the king, has taken shape. How did the way of educating the ruling class change in the course of time? And what was the role of culture? This proverb seems to offer a few significant hints, starting from its keyword illitteratus, that, by slowly changing its meaning, from ‘uneducated’ to ‘ignorant’ and ‘vulgar’, caused the semantic variation of the whole sentence and that of the triangular relationship between history, knowledge and power.