Whilst forming the central feature of the ritualistic symbolism, this triad--Prajapati, sacrifice (oblation, victim), sacrificer--is extended in various ways. An important collateral identification is that of Prajapati (and the sacrificer) with Agni, the god of fire, embodied not only in the offering-fire, but also in the sacred Soma-altar, the technical name of which is _agni_. For this reason the altar, as representative of the universe, is built in five layers, representing earth, air and heaven, and the intermediate regions; and in the centre of the altar-site, below the first layer, on a circular gold plate (the sun), a small golden man (_purusha_) is laid down with his face looking upwards. This is Prajapati, and the sacrificer, who when regenerated will pass upwards through the three worlds to the realms of light, naturally perforated bricks being for this purpose placed in the middle of the three principal altar-layers. One of the fourteen sections of the Satapatha-brahmana, the tenth, called _Agni-rahasya_ or "the mystery of Agni (the god and altar)," is entirely devoted to this feature of the sacrificial symbolism. Similarly the sacrificer, as the human representatiye of the Lord of Creatures, is identified with Soma (as the supreme oblation), with Time, and finally with Death: by the sacrificer thus becoming Death himself, the fell god ceases to have power over him and he is assured of everlasting life. And now we get the Supreme Lord in his last aspect; nay, his one true and real aspect, in which the sacrificer, on shuffling off this mortal coil, will himself come to share--that of pure intellectuality, pure spirituality--he is Mind: such is the ultimate source of being, the one Self, the Purusha, the Brahman. As the sum total of the wisdom propounded in the mystery of Agni, the searcher after truth is exhorted to meditate on that Self, made up of intelligence, endowed with a body of spirit, a form of light, and of an ethereal nature; holding sway over all the regions and pervading this All, being itself speechless and devoid of mental states; and by so doing he shall gain the assurance that "even as a grain of rice, or the smallest granule of millet, so is the golden Purusha in my heart; even as a smokeless light, it is greater than the sky, greater than the ether, greater than the earth, greater than all existing things;--that Self of the Spirit is my Self; on passing away from hence, I shall obtain that Self. And, verily, whosoever has this trust, for him there is no uncertainty." (J. E.)