Specialised type of mandala or geometric diagram, used in Tantric worship in Hinduism, Buddhism and Jainism. A yantra (Sanskrit, ‘instrument’) is an abstract representation of a particular deity and may be used as a tool for meditation (dhyanayantra), a base for ritual (sthapanayantra), an image for regular worship (pujayantra), in magical rites for various spiritual or material purposes, or as a talisman. Compared to mandalas, yantras are typically smaller, less colourful, generally show no figural images, and are often mobile, though sometimes installed at places of worship. A yantra may be a diagram, drawn on materials such as paper, cloth, bone or skin, or a three-dimensional structure, usually made of metal. Yantra design features various geometric shapes — most commonly inverted triangles, upright triangles, and hexagrams, symbolising respectively the yoni, lingam, and the union of the two — arranged in a pattern around a central dot or bindu symbolising the point of spiritual emanation. These are typically bounded by lotus petals and a square representing the four cardinal directions. A sriyantra is an especially elaborate yantra showing nine interlocking triangles.