One other feature of Sectarian Hinduism must be mentioned. It may be described as Tantrism or, in one of its aspects, as the later Yoga and is a combination of practices and theories which have their roots in the old literature and began to form a connected doctrine at least as early as the eighth century A.D. Some of its principal ideas are as follows: (i) Letters and syllables (and also their written forms and diagrams) have a potent influence both for the human organism and for the universe. This idea is found in the early Upanishads[437] and is fully developed in the later Sectarian Upanishads. (ii) The human organism is a miniature copy of the universe.[438] It contains many lines or channels (nâḍî) along which the nerve force moves and also nervous centres distributed from the hips to the head, (iii) In the lowest centre resides a force identical with the force which creates the universe.[439] When by processes which are partly physical it is roused and made to ascend to the highest centre, emancipation and bliss are obtained. (iv) There is a mysterious connection between the process of cosmic evolution and sound, especially the sacred sound _Om._ These ideas are developed most thoroughly in Śâktist works, but are by no means peculiar to them. They are found in the Pâncarâtra and the later Puranas and have influenced almost all modern sects, although those which are based on emotional devotion are naturally less inclined to favour physical and magical means of obtaining salvation. FOOTNOTES: [Footnote 401: The population of India (about 315 millions) is larger than that of Europe without Russia.] [Footnote 402: But compare the English poet "Flower in the crannied wall, I pluck you out of the crannies, ... but if I could understand What you are, root and all, and all in all I should know what God and man is."] [Footnote 403: Efforts are now being made by Hindus to suppress this institution.] [Footnote 404: In the Vedic funeral ceremonies the wife lies down by her dead husband and is called back to the world of the living which points to an earlier form of the rite where she died with him. But even at this period, those who did not follow the Vedic customs may have killed widows with their husbands (see too Ath. Veda, XII. 3), and later, the invaders from Central Asia probably reinforced the usage. The much-abused Tantras forbid it.]