The application of bhasma or ashes forms an integral part of tattva shuddhisadhana, as it is a symbol of physical purification, as well as subtle and causal realms. Mahayogi Shiva, who is considered to be the father of tantra, is depicted naked and his whole body is besmeared with bhasma. Thus it is considered to be an auspicious act of discovering your shiva nature.
In the Chandogyopanishad it is stated that the five tattvas have evolved from the mind,the mind has evolved from prana and prana has evolved from pure consciousness. Thus the tattvas are present in every form of creation. In the physical body, they manifest as chitta shakti, prana shakti and atma shakti, which act on the body and mind through energy channels or nadis and the breath or swara.