“When Svetaketu was twelve years old, he was sent to a teacher with whom he studied until he was twenty-four. After learning all the Vedas, he returned home full of conceit in the belief that he was consummately well-educated, and very censorious.
His father said to him, "Svetaketu, my child, you are so full of your learning and so censorious, have you asked for that knowledge by which we hear the unhearable, by which we perceive what cannot be perceived and know what cannot be known?" "What is that knowledge, sir?" asked Svetaketu.
His father replied, "As by knowing one lump of clay all that is made of clay is known - so, my child, is that knowledge, knowing which we know all."
"But surely these venerable teachers of mine are ignorant of this knowledge; for if they possessed it they would have imparted it to me. Do you, sir, therefore, give me that knowledge?"
"So be it," said the father... And he said, "Bring me a fruit of the nyagrodha tree." "Here it is, sir." "Break it." "It is broken, sir." "What do you see there?" "Some seeds, sir, exceedingly small." "Break one of these." "It is broken, sir." "What do you see there?" "Nothing at all."
The father said, "My son, that subtle essence which you do not perceive there - in that very essence stands the being of the huge nyagrodha tree. In that which is the subtle essence of all that exists has its self. That is the True, that is the Self, and thou Svetaketu art That."
"Pray, sir", said the son, "tell me more." "Be it so, my child", the father replied; and he said, "Place this salt in water, and come to me tomorrow morning."
The son did as he was told.
Next morning the father said, "Bring me the salt you put in the water."
The son looked for it, but could not find it, for the salt, of course, had dissolved.
Tha father said, "Taste some of the water from the surface of the vessel. How is it?" "Salty." "Taste some from the middle. How is it?" "Salty." "Taste some from the bottom. How is it?" "Salty."
The father said, "Throw the water away and then come back to me again."
The son did so; but the salt was not lost, for the salt existed forever.
Then the father said, "Here likewise in this body of yours, my son, you do not perceive the True; but there, in fact, it is. In that which is the subtle essence, all that exists has its self. That is the True, that is the Self, and thou, Svetaketu, art That."
-Chandogya Upanishad.