Plutarch, Demetrius
Bernadotte Perrin, Ed.

18. Upon this, the multitude for the first time saluted Antigonus and Demetrius as kings. Antigonus, accordingly, was immediately crowned by his friends, and Demetrius received a diadem from his father, with a letter in which he was addressed as King. The followers of Ptolemy in Egypt on their part also, when these things were reported to them, gave him the title of King, that they might not appear to lose spirit on account of their defeat. [2] And thus their emulation carried the practice among the other successors of Alexander. For Lysimachus began to wear a diadem, and Seleucus also in his interviews with the Greeks; with the Barbarians he had before this dealt as king. Cassander, however, although the others gave him the royal title in their letters and addresses, wrote his letters in his own untitled name, as he had been wont to do.

[3] Now, this practice did not mean the addition of a name or a change of fashion merely, but it stirred the spirits of the men, lifted their thoughts high, and introduced into their lives and dealings with others pomposity and ostentation, just as tragic actors adapt to their costumes their gait, voice, posture at table, and manner of addressing others. [4] Consequently they became harsher in their judicial decisions also; they laid aside that dissemblance of power which formerly had often made them more lenient and gentle with their subjects. So great influence had a flatterer's single word, and with so great a change did it fill the whole world.