Yantras may be simple designs such as the cross, triangle, square, circle or lotus pattern, symbolizing basic concepts, or may be more complex combinations of such elements in figures representing in abstract form the particular creative forces in the cosmos which are called divinities. they are closely related to the mandalas used by both Hindu and Buddhist Tantrism, in which geometric design is supplemented by elaborate symbolic images of the deities which by their various forms and attributes indicate different aspects of the hidden order of reality. As Mircea Eliade says, the yantra is 'the linear paradigm of the mandala', expressing the same principles in geometric form. Like mandalas, yantras are used in the context of meditation and worship as visual-aids to concentration of the mind leading to realization of abstract principle which is the inner meaning of the visible representation.
The best known and geometrically the most complex yantra is the Sri-yantra, also known as the Sri-yantra, employed by the Sakta school of Tantrism which visualizes the divine primarily in female form. The structure of this yantra is enigmatically described in the Saundarya-lahari (The Wave of Beauty), a lengthy poem praising the great goddess whose dwelling place the Sri-yantra is said to be:
By reason of the four Srikanthas (srikantha is an
epithet of Siva) and the five damsels of Siva (which have
the nature of Sakti), which are penetrated by Sambhu (i.e. bindu- the
dot in the centre) and constitute the nine fundamental natures, the 43
(or 44) angles of your dwelling place are evolved, along
with the 8-petalled and 16-petalled lotuses, the circles and
the three lines. (stanza 11)
The diagram may be more accurately described as a bilaterally symmetrical figure composed of nine interwoven isosceles triangles, usually depicted with five triangles pointing downwards and four pointing upwards. The former are said to correspond to the yoni representing the dynamic female principle of energy (Sakti), while the latter correspond to the linga representing the static male principle of wisdom (Siva). (The Buddhist Tantrics, incidentally, regard the male principle as dynamic and the female as static.) The central dot called bindu represents the original unity of the male and female principles prior to creation and the paradoxical point female principles prior to creation and the paradoxical point from which the manifestation of the cosmos emerges. The interpenetration of the nine basic triangles gives rise to a number of subsidiary triangles (43 including the central triangle enclosing the bindu) which form the abodes of the deities, representing the particularization of the original creative forces into more concrete manifestations. Sometimes the names of deities and Sanskrit syllables are written into these triangles, or images of the deities are placed in them.
In most versions of the yantra this central design
is enclosed by two circular lotus-patterns with eight
and sixteen petals, a girdle of three concentric circles, and finally a
square arrangement of straight line ('the three lines') with four
openings or 'doors' at the cardinal points called 'World House'
(bhugra). This square outline, which is common also to mandalas,
symbolizes the royal palace in which the deities reside - an area of
sacred space protected from the disintegrating forces of chaos. In general, the Sri-yantra is a
'cosmogram' - a graphic representation of the universal processes of
emanation and reabsorption reduced to their essential outline. As Eliade
puts it, the yantra: 'An expression in terms of linear symbolism of the
cosmic manifestations, beginning with the primordial unity.'