Notes to Macbeth, Act 3, Scene 1, lines 54-56: "under him, / My Genius is rebuked as, it is said, / Mark Antony's was by Caesar"

Act 3, Scene 1, line 54.
In Shakespeare's Antony and Cleopatra a soothsayer tells Antony that "Thy daemon, that thy spirit which keeps thee, is / Noble, courageous, high unmatchable, / Where Caesar's is not; but near him thy angel / Becomes a fear, as being o'erpow'r'd." Antony has to admit that the soothsayer is right.