Wisdom from the Early Cynics, Antisthenes 7

And he used to taunt Plato with being conceited. 

At all events when in a procession he spied a spirited charger he said, turning to Plato, "It seems to me that you would have made just such a proud, showy steed." This because Plato was constantly praising horses. 

And one day he visited Plato, who was ill, and seeing the basin into which Plato had vomited, remarked, "The bile I see, but not the pride."

—Diogenes Laërtius, 6.7