Regum et imperatorum apophthegmata

Plutarch

Plutarch. Moralia, Vol. III. Babbitt, Frank Cole, translator. Cambridge, MA: Harvard University Press; London: William Heinemann Ltd., 1931 (printing).

Demetrius of Phalerum recommended to Ptolemy the king to buy and read the books dealing with the office of king and ruler. For, as he said, those things which the kings’ friends are not bold enough to recommend to them are written in the books.