Chapter VI Sloka 19

ywa dIpae invatSwae ne¼te saepma Sm&ta,
yaeignae yticÄSy yuÃtae yaegmaTmn>.

yath˜ deepo niv˜tastho 
neðgate sopam˜ sm®t˜ |
yogino yatacittasya 
yuñjato yogam˜tmana× ( 6|19)||

As a lamp placed is a windless spot does not flicker - to such is compared the Yogi of controlled mind, practising Yoga in the Self (or absorbed in the Yoga of the Self).

Commentary: This is a beautiful simile. Yogins quote this simile very often when they talk of concentration or steadiness or one-pointedness of the mind. A steady mind will serve as a powerful searchlight to find out the hidden spiritual treasures of the Self.