A yantra is a geometric diagram used as a support for meditation and worship, built from interlocking triangles, lotus petals, circles and a square enclosure with four gates.
Form and use
The best known is the Sri Yantra, nine interlocked triangles that generate forty-three smaller ones around a central point, and one of the more demanding constructions in the corpus. A yantra is normally engraved on metal, consecrated and installed, and in temple practice it may sit beneath the image rather than in view. Its use is generally tied to a specific mantra and to initiation from a teacher, so the diagram is not a free-standing decoration but the visible half of a transmitted practice.
What is public and what is not
What a yantra is and what it is for can be described openly: it is a map of the deity and the cosmos, a focus that draws the worshipper's attention inward to a centre. The consecration procedures and the mantras attached to a given yantra, however, belong to the line of teaching that confers them and are not set out here. The tradition draws that boundary itself, treating the outward form as describable and the empowerment as something received rather than read from a page.