As soon as one has seen a jar with intoxicating liquor, women with a red colour, a lion, a corpse, a red lotus, a fight between a tiger and an elephant, one's guru or the king, one should bow to Mahamaya - Kalika Purana, van Kooij translation.
This chapter of an ancient text attributed to Siddha Matsyendranath, said to be the founder of the Natha lineage, deals with the characteristics of the linga and discusses the flowers, centres or chakras within the body in the light of the Yogini Kaula tradition.
A translation of the entire text is in print. It is an important text because it seems to unite the earlier Siddha tradition with the Natha tradition, and Matsyendranath expounds the Yogini Kaula line.
The topic deals with, amongst many other familiar Kaula topics, the 64 yoginis and the different sacred sites (pitha) held important in both this and later tantras.
Devi said - Great Lord, I have questions concerning the characteristics of Kula, the Self, and consciousness chiefly. Be gracious, O Shankara Nath ! (1 )
Bhairava said - Listen with concentrated mind to the characteristics of Kula. Where there is mind, there too are the senses, the sense objects and the body - these are permeated by one's own Shakti, one's embodied being, and the (five) elements. (2-3)
It is said that the place and inner part of meditation is a clear understanding of puja. All proceeds from the letters (of the alphabet), and in this is voidness. (4)
Dearest, (in the pinda exist) the (cakras) of five lines, 16 lines, sixty four petals, the truly beautiful 100 petal (lotus) and the beautiful thousand petal lotus and above this is a very brilliant 10,000,000 petal lotus. Above the 10,000,000 petal lotus is a 30,000,000 petal lotus, each pericarp of which is similar to a flame. Above this is the all encompassing, eternal, undivided, independent, steady lotus- pervading all, stainless. By its will (sveccha) it causes creation and dissolution. Both the animate and inanimate are dissolved in this linga. (5-10)
It is the all-pervading sphere, still, without Kalas. It should be understood that being lettered (implies) ignorance of this, whilst one who has come to know this is liberated from the fetters. It is destitute of both mind and non-mind, free of meditation and dharana. Clearly it bestows all, is eternal, like an atasi flower, the divine essence having both colour and colourless, attained only by knowledge, through being in the line of succession (parampara). (11-13)
Devi, the characteristics of the Kula Laksha have been declared - that linga which is not made of wood, stone, clay, jewel, brass, gold, iron, copper, crystal, clay, tin, lead or copper - which gives rise to the various blossomings of the red flowers, worshipped by all the worlds. (14-15)
Devi, one should not concern oneself with the eighteen lokasastras such as adhyatmika and so forth. Mahdevi, this (sort of preoccupation) is the cause of a person being a pashu, devoid of knowledge. All people on the path of spiritual knowledge (divyas) should not associate with the ignorant, those on useless paths, devoid of Kula knowledge. (15-18)
Brahma and so forth, all the gods and asuras, the saintly, yakshas, gandharvas, siddhas, plants, trees, insects, planets, sidereal constellations, stars and all the rest, all which is in the cosmos - either moving or fixed, elements and so forth, all manifest from the centre of the bindu. (19-20)
This linga, the cause of both creation and dissolution, worshipped by siddhas, shining by its own light, pure, eternal, completely immeasurable, is like the flame which is the fire (at the end of time), like lightning in the sky. One becomes liberated after knowing and perceiving this boon giving linga. (21-22)
This linga is eternally erect, a vajra linga, and my not be destroyed by raging fire, landslide, or torrent. ( 23)
Devi, a Kaulika should worship this to achieve the wished for siddhi, employing mental flowers, sweetly scented incense and so forth. (24)
The first flower is non-harmfulness, the second sense restraint, the third generosity, the fourth right disposition, the fifth compassion, and the sixth freedom from cruelty. The seventh flower is meditation, and the eighth flower is knowledge. Knowing these rules relating to flowers, one should worship this mental linga. (25-26)
Worshipping this body linga, one may obtain both liberation and enjoyment. Devi, it is the linga giving siddhi, stationed in the body, steady and strong. Whosoever should always meditate on this mental linga, for such a one is achieved the pre-eminent and highest self knowledge. (26-28)
Thus, O Devi, have been declared the characteristics of the Kaulika body lingam. Any other (external linga) one should abandon, such as those made of stone, wood or clay. The ordinary path is devoid of success and liberation. (28-30)
The inner meaning of this, placed in the body, belongs to the Kula Agama. Whosoever takes the meaning as placing (a linga) outside himself enters the arena of pashus. (31)
Devi, the inner meaning of this knowledge has been declared to you. One should never give it to the undevoted, but only to devoted persons. (32)