A yantra is a mystical diagram that is the house in which a Devata (God or Goddess) dwells. Worship of planetary yantras is used to remove the ill effects of malefic planets and to increase the positive influences of favorable planets.
Buddha is the God of Mercury, and is one of the nine primary celestial beings in Hindu Vedic astrology who are the agents of the Law of Karma.
The yantra shows Mercury's symbol, the zodiac signs that Mercury rules, and mantras associated with the ruling deity, Buddha Deva. Mercury is the great messenger of the Gods. He represents speech, communication and commerce on all levels.