The Sri Yantra, or Shri Chakra, is the most celebrated of the yantras, the geometric diagrams used in Tantric Hindu worship and meditation. It is composed of nine interlocking triangles, four pointing up, associated with Shiva, and five pointing down, associated with Shakti, overlaid so as to generate forty-three smaller triangles around a central point, the bindu. These are enclosed by a double ring of lotus petals, a threefold girdle and a square outer enclosure with four gates. It is the yantra of the goddess Tripura Sundari in the Shri Vidya tradition, and its construction to exact proportion is itself a demanding geometric problem: the nine triangles must intersect so that every crossing point lines up correctly, and mathematicians who have tried to specify the figure exactly, rather than by eye, have found the constraints resist a fully consistent flat solution.
A 1998 study by C. S. Rao mapped the diagram onto a curved, sphere-like surface and showed every one of its constraints belongs to a single restricted family of functions, work read by some as suggesting the flat, drawn Sri Yantra is necessarily an approximation of a figure that is truly consistent only when allowed a small degree of curvature.