Letters 80.10

Do you see yonder Scythian or Sarmatian king, his head adorned with the badge of his office? If you wish to see what he amounts to, and to know his full worth, take off his diadem; much evil lurks beneath it. But why do I speak of others? If you wish to set a value on yourself, put away your money, your estates, your honours, and look into your own soul. At present, you are taking the word of others for what you are. Farewell.

Seneca, Letters to Lucilius 80.10, translated by Richard Mott Gummere