"The word yoga is met for the first time in Vedas in the Katha Upanishad and some description of it is contained in Svetasvatra, the last of the early Upanishads. It is more frequently met with in Puranas, the epics and other later literature, and is sometimes synonymously used for tapa and dhyana (i.e., religious austerity and meditation). Basically Yoga is nothing more or less than systematized concentration. Fixity of attention, whether on a God or a Goddess, on a symbol or a diagram, on the void or any material object, or whether on a mantra or any particular region of the body, is the main exercise of every ancient form of Yoga."