The Yogatattwa Upanishad warns against the misuse of mantra.
In the w:UpanishadTarasara Upanishad, Yagnyavalkya teaches Bharadwaja the right use of a certain mantra – aum -namo –narayanaaya - which consists of eight syllables. Each separate syllable symbolizes aspects of Transcendence ( Brahma , Vishnu , etc) or archetypal MIND energies.
Mantra Upanishad: These teachings center on esoteric interpretations of specific sounds and syllables and place those interpretations into Yogic as well as Saiva , Vaishnava , and Durga theistic contexts. Typical of these works are Tarasara, Kalisantarana, and Narayana Upansihad.
Shanti – peace - is a most essential quality expressed in the ancient Vedic texts of the Upanishads. It is invoked at the beginning and the end of each Upanishad chapter.
There is group of special shanti mantras found in vedic texts, such as the Upanishads. At he close of each Upanishad chapter, for instance, the word shanti is chanted three times, as a mantra. This is to remove the three kinds of suffering – personal, external and atmospheric
Theories had been propounded and repeated, others had been taken up, until at last the idea of Maya became fixed. We read in the Shvetashvatara Upanishad, "Know nature to be Maya and the Ruler of this Maya is the Lord Himself." Coming to our philosophers, we find that this word Maya has been manipulated in various fashions, until we come to the great Shankaracharya.
There is no kind of framework within which we can find consciousness in the plural; this is simply something we construct because of the temporal plurality of individuals, but it is a false construction....The only solution to this conflict insofar as any is available to us at all lies in the ancient wisdom of the Upanishad.