Regum et imperatorum apophthegmata
Plutarch
Plutarch. Moralia, Vol. III. Babbitt, Frank Cole, translator. Cambridge, MA: Harvard University Press; London: William Heinemann Ltd., 1931 (printing).
Parysatis, the mother of Cyrus and Artaxerxes, advised that he who was intending to talk frankly with the king should use words of softest texture.