In the Brhadaranyaka Upanishad there is the metaphor of a spider sitting at the center of its web, issuing and reabsorbing its threads in concentric circles, all held at one point. The spider’s threads symmetrically expand into a visible circumference, but they can all be traced back to the central point of the web.
Like the spider in its web, the center of the yantra is the power-point from which the entire diagram expands, the radiating source of energy that generates all forms. It is the divine essence out of which proceeds the polarized world. It is called Bindu, the first drop, which spreads unfolds, and expands into the tangible realm of the universe. Indeed the optical focus of the yantra is always its center, from which the force lines radiate outwards in concentric circles and dissolve in the outer circumference. On a metaphysical level the Bindu represents the unity of the static (male, Shiva) and the kinetic (female, Shakti) cosmic principles, which expand to create the infinite universe of matter and spirit. A meeting-ground of subject and object, this is exactly the kind of spiritual oneness that the tantra artist strives for. A region where art and artist, creator and viewer merge into a single identity, becoming one with the cosmos as a whole. In the final meditation on the yantra, the Bindu is the region where the ultimate union of the aspirant with the divine takes place.
For the successful creation of a yantra, the artist must look beyond appearances and penetrate to the essence. The center, by virtue of being a dot of zero dimensions, is visualized as the ultimate entity beyond which a thing or energy cannot be contracted or condensed. This infinite reservoir of collective energy is the supremely creative nucleus, and therefore is the repository of all manifestation. As a center, it controls everything which is projected from it; hence it is also called MahaBindu, or the Great Point. It is indeed the starting point of the mental quest for salvation and also the ultimate point in this journey.
According to another school of logic, when a non-manifest stage of existence becomes manifest, its manifestation must begin somewhere, in some point of space, at some point of time. There must be an instant when it has not yet any extension but has begun to have location. According to this interpretation, the first instant when a thing does not yet exist and yet has already begun is adequately represented by the dimensionless point.
The Bindu thus contains within itself the two poles’ (zero and infinity) and all that lies between. Its inherent energy contains all potentialities and all polarities. In the actual creative process, the Bindu evolves with the help of straight lines into the trikona (triangle).
Text from Tantra – The Art of Philosophy