Chandogya Upanishad
Prapathaka VI, Khanda 13
'Place this salt in water, and then wait on me in the morning.' The son did as he was commanded. The father said to him: 'Bring me the salt, which you placed in the water last night.' The son having looked for it, found it not, for, of course, it was melted.
The father said: 'Taste it from the surface of the water. How is it?' The son replied: 'It is salt.' 'Taste it from the middle. How is it?' The son replied: 'It is salt.' 'Taste it from the bottom. How is it?' The son replied 'It is salt.' The father said Throw it away and then wait on me.' He did so; but salt exists for ever. Then the father said: 'Here also, in this body, forsooth, you do not perceive the True (Sat), my son; but there indeed it is.