Mantras are mystic syllabus or formulae supposed to be endowed with supernatural powers. According to some tāntrik works, mantras can be classified into two groups: the Saguṇa-mantras and the Brāhma-mantras.
The former are connected with the Saguṇa Brahman (Brahman with attri-butes) and the latter with the Nirguṇa Brahman (Brahman without attributes). Whereas upāsanā or meditation with the former leads to savikalpa-samādhi (samādhi in which the mind takes the form of the deity and results in its reali-zation), upāsanā with the latter results in nirvikalpa-samādhi (samādhi in which the formless Brahman is experienced).
The well-known mahāvākyas (‘great sentences’) culled from the Upaniṣads chosen from the four Vedas are classed under Brāhma-mantras. The number of the Brāhma-mantras may vary from 12 to 1,80,000. The Gāyatrī-mantra has been described as the best of the Brāhma-mantras.