"In Hindu devotional tradition, “yantra” is the general term for instruments of worship, namely, idols, pictures, or geometrical diagrams. A yantra may serve as a (1) representation of some personification or aspect of the divine, (2) a model for the worship of a divinity immediately within the heart after the paraphernalia of outward devotion (idols, perfumes, offerings, audibly uttered formulae) have been discarded by the advance initiate, (3) a kind of chart or schedule for the gradual evolution of a vision, while identifying the Self with its slowly varying contents that is to say, with divinity in all its phases of transformation. In this case the yantra contains dynamic elements."