Instead of trying to meditate on the pure subject, what is done is try to steal the mind on the form of the chosen deity. Sri Ramakrishna: Normally the worldly names and forms diverte us from the Atman. They pull our mind out into the world but this divine name and form does not obscure the nature of the atman.
Swami Sarvapriyananda teaches the Katha Upanishad, one of India's most revered texts which is also a part of the Vedas. It is a collection of philosophical poems representing a conversation between the sage Naciketas and Yama (god of death). They discuss the nature of Atman, Brahman and Moksha(liberation).