This word in its most general sense means an instrument, or that by which anything is accomplished. In worship it is that by which the mind is fixed on its object. The Yogini Tantra says that the Devi should be worshipped either in pratima (image), mandala, or yantra. At a certain stage of spiritual progress the sadhaka is qualified to worship yantra. The siddha-yogi in inward worship (antar-puja) commences with the worship of yantra, which is the sign (sangketa) of brahma-vijnana as the mantra is the sangketa of the Devata. It is also said that yantra is so called because it subdues (niyantrana) lust, anger, and the other sins of jiva and the sufferings caused thereby. This yantra is a diagram engraved or drawn on metal, paper, or other substances, which is worshipped in the same manner as an image (pratima). As different mantra are prescribed for different worships, so are different yantra. The yantras are therefore of various designs, according to the object of worship. The cover of this work shows a silver Gayatri yantra belonging to the author. In the centre triangle are engraved in the middle the words, Shri Shri Gayatri sva-prasada siddhing kuru (Shri Shri Gayatri Devi: grant me success), and at each inner corner there are the vija Hring and Hrah. In the spaces formed by the intersections of the outer ovoid circles is the vija Hring. The outside circular band contains the vija Tha which indicates Svaha, commonly employed to terminate the feminine mantra or vidya. The eight lotus petals which spring from the band are inscribed with the vija, Hring, Ing, Hrah. The outermost band contains all the matrika, or letters of the alphabet, from ankara to laksha. The whole is enclosed in the way common to all yantra by a bhupura, by which, as it were, the yantra is enclosed from the outer world. The yantra when inscribed with mantra, serves (so far as these are concerned) the purpose of a mnemonic chart of the mantra appropriate to the particular Devata whose presence is to be invoked into the yantra. Certain preliminaries precede, as in the case of a pratima, the worship of a yantra. The worshipper first meditates upon the Devata, and then arouses Him or Her in himself. He then communicates the divine presence thus aroused to the yantra. When the Devata has by the appropriate mantra been invoked into the yantra, the vital airs (prana) of the Devata are infused therein by the prana-pratishtha ceremony, mantra, and mudra. The Devata is thereby installed in the yantra, which is no longer mere gross matter veiling the spirit which has been always there, but instinct with its aroused presence, which the sadhaka first welcomes and then worships. Mantra in itself is Devata, and yantra is mantra in that it is the body of the Devata who is mantra.