A strange religious feature pointing to a remote antiquity is the occasional deification and worship even of objects fashioned by the hand of man, when regarded as useful to him. These are chiefly sacrificial implements. Thus in one hymn (iii. 8) the sacrificial post (called "lord of the forest") is invoked, while three hymns of the tenth book celebrate the pressing stones used in preparing soma. The plough is invoked in a few stanzas; and an entire hymn (vi. 75) is devoted to the praise of various implements of war, while one in the Atharva-veda (v. 20) glorifies the drum. The demons so frequently mentioned in the Rigveda are of two classes. The one consists of the aërial adversaries of the gods. The older view is that of a conflict waged between a single god and a single demon. This gradually developed into the notion of the gods and the demons in general being arrayed against each other as two opposing hosts. The Brahmanas regularly represent the antagonism thus. Asura is the ordinary name of the aërial foes of the gods. This word has a remarkable history. In the Rigveda it is predominantly a designation of the gods, and in the Avesta it denotes, in the form of Ahura, the highest god of Zoroastrianism. In the later parts of the Rigveda, however, asura, when used by itself, also signifies "demon," and this is its only sense in the Atharva-veda. A somewhat unsuccessful attempt has been made to explain how a word signifying "god" came to mean "devil," as the result of national conflicts, the Asuras or gods of extra-Vedic tribes becoming demons to the Vedic Indian, just as the devas or gods of the Veda are demons in the Avesta. There is no traditional evidence in support of this view, and it is opposed by the fact that to the Rigvedic Indian asura not only in general meant a divine being, but was especially appropriate to Varuna, the most exalted of the gods. The word must therefore have changed its meaning in course of time within the Veda itself. Here it seems from the beginning to have had the sense of "possessor of occult power," and hence to have been potentially applicable to hostile beings. Thus in one hymn of the Rigveda (x. 124) both senses seem to occur. Towards the end of the Rigvedic period the application of the word to the gods began to fall into abeyance. This tendency was in all likelihood accelerated by the need of a word denoting the hostile demoniac powers generally, as well as by an incipient popular etymology, which saw a negative (a-sura) in the word and led to the invention of sura, "god," a term first found in the Upanishads.