Chandogya Upanishad
... that by knowing an object it can be known, and any differences are words and the object is reality. To this the son was confused, so he asked for further explanation. The father, in order to try to explain to his son, tells his son to get the fruit of the banyan tree and break it. Upon doing this, the father asks his son what it is that he saw; the son replies “tiny seeds”. The father then tells him to break the seeds and tell him what it is that he saw, and the son replies “nothing”. To this the father informs the son that even though you cannot see something, if its essence is invisible, it is still truth. This subtle essence is the Spirit of the whole universe. That is Reality. That is Atman. To this example the son asks the father to explain more. So the father asked his son to place salt in water and bring it to him the next day. The son brought the glass to the father and looked in it and told his father that he could not find the salt that he had placed in the glass. The father asked him to drink from each side of the glass and from the middle and tell him what he tasted. The son replied by saying “salt”. The father told him to look for the s...