Juno, Queen of the gods, had the fairest cow that anyone ever saw. The creature was creamy white, and her eyes were as soft and bright a blue as those of any maiden in the world. Juno and Jupiter, the King of the gods, often played tricks on each other, and Juno knew well that the King would try to get her cow. There was a watchman named Argus and one would think that he could see all that was going on in the world, for he had a hundred eyes, and no one had ever seen them all asleep at once. For this reason, Queen Juno gave to Argus the work of watching over her beloved white cow.
However, the King of the gods knew what she had done, and he laughed to himself and said, “I will play a trick on Juno, and I shall have the white cow.” He sent for his youngest son named Mercury and whispered in his ear, “Go to the green field where Argus watches the cream-white cow and bring her to me.”
Mercury was always happy when he could play a ruse on anyone, and he set out gladly for the field where Argus safeguarded the cream-white cow with every one of his hundred eyes.
Now Mercury could tell merry tales of all that went on in the world. He could sing, too, and the music of his voice had lulled many a god to sleep. Argus knew this, but he had been alone for such a long time, and he thought, “What harm is there in listening to his lively chatter? I have a hundred eyes, and even if half of them were to doze, the others could easily keep watch over one cow.” And so he gladly hailed Mercury and said, “I have been alone in this field a long, long time, but you have roamed about as you would. Will you not sing to me, and tell me what has happened in the world? You too would be glad to hear stories and music, if you had nothing to do but watch a cow, even if it was the cow of a queen.”
So, Mercury sang and told stories. Some of the songs were merry, and some were sad. The watchman closed one eye, then another and another, but there were two eyes that would not close for all the sad and merry songs in the world. Then, Mercury drew forth a hollow reed that he had brought from the river and began to play on it. It was a reed infused with magic and, as he played, one could hear the water rippling gently on the shore and the breath of the wind in the pine-trees; one could see the lilies bending their heads as the dusk came on, and the stars twinkling softly in the Summer sky.
It is no wonder that Argus closed one eye and then the other. Every one of his hundred eyes was fast asleep, and Mercury went away gleefully to the King of the gods with the cream-white cow.
Juno had so often played tricks on the King that he was happy to have played this one on her, but Juno was furious, and she said to Argus, “You are a strange watchman. You have a hundred eyes, and yet you could not keep even one of them from falling asleep. My peacock is wiser than you, for he knows when anyone is watching him. Therefore, I shall take your one-hundred eyes and place them in the tail of the peacock!”
And so today, whoever looks at the peacock can count in his tail the hundred eyes that once belonged to Argus.
— Why The Peacock’s Tail Has A Hundred Eyes, by Florence Holbrook.