When Rabbi Shlomo of Karlin drank tea or coffee, he would take a lump of sugar and hold it in his hand while he drank.
His son once asked:
– Dad, why are you doing this? If you need sugar, put it in your mouth, and if you don’t need it, why hold it in your hand?
-When he finished drinking, Rabbi Shlomo gave this lump of sugar to his son and said:
– Try it!
The son took it, put it in his mouth and was surprised, not tasting any sweetness.
Subsequently, when his son talked about this, he said:
– One who has cognized the unity of everything can taste the taste with his hand as with a tongue.
Source: https://pritchi.ru/id_10215