mantra could be interpreted as "the glorious words". The mantras are given a great position in spirituality. These mantras are to be chanted very many times as they have great power in them, which could be used to elevate oneself spiritually. The glorious mahA mantra na maH shi vA ya is one of the Holy Five Syllables held with great esteem by the devotees of the God. If this yogic scripture itself is called thirumanthiram, it signifies the glory of this text.

This is tenth one in the Tamil Shaivite thirumuRais (1). Of all the thirumuRais it deals extensively and explicitly with the philosophical aspects. Because of this it is called the shastra by the thirumuRai followers. This was given to us as a boon by the great yogi saint thirumUlar (2). He transmigrated from his original body to the body of a cowherd man called mUlan and composed these highly rich hymns. In these the saint has given the essence of the highly revered Shaiva tantra texts Agamas. Through his songs we get to know that there are 28 Agamas given by the God and he got through his guru 9 Agamas. The themes of these nine Agamas have been given as nine tantras in this scripture. The nine Agamas he mentions are

1. kAraNAgamam
2. kAmikAgamam
3. vIrAgamam
4. chintyAgamam
5. vAtulAgamam
6. vyAmalAgamam
7. kAlottarAgamam
8. suprbhedAgamam
9. makuTAgamam

This yogi sat in the shade of the peepul (arasu) tree and gave one song per annum and thus 3000 songs !

The hymns in this holy text are at places very simple to understand and at other places are really tough ones and in some other places they look very simple superficially but actually have a very cryptic deep meaning ! So this is a feast for enjoying bit by bit contemplating through its spiritual values.

Continued Here Brief of the tantras in thirumandhiram.

See Also: 
1. 12 thirumuRais
2. thirumoolar