the precept "seek Self-knowledge which is Highest Bliss", and expounds on this premise like the other primary Upanishads of Hinduism. The detailed teachings of Katha Upanishad have been variously interpreted, as Dvaita (dualistic) and as Advaita (non-dualistic). The Katha Upanishad found in the Yajurveda is among the most widely studied Upanishads. Philosophers such as Arthur Schopenhauer praised it, Edwin Arnold rendered it in verse as "The Secret of Death", and Ralph Waldo Emerson credited Katha Upanishad for the central story at the end of his essay Immortality, as well as his poem "Brahma". Shvetashvatara Upanishad The Shvetashvatara Upanishad is found in the black Yajurveda. The text opens with metaphysical questions about the primal cause of all existence, its origin, its end, and what role if any did time, nature, necessity, chance, the spirit had as primal cause? It then develops its answer, concluding that "the Universal Soul exists in every individual, it expresses itself in every creature, everything in the world is a projection of it, and that there is Oneness, a unity of souls in one and only Self". The Shvetashvatara Upanishad is notable for its discussion of the concept of personal god – Ishvara, and suggesting it to be a path to one's own Highest Self. The text is also notable for its multiple mentions of both Rudra and Shiva, along with other Vedic deities, and of crystallization of Shiva as a central theme. Maitrayaniya Upanishad The Maitrayaniya Upanishad, also known as the Maitri Upanishad, is found in the black Yajurveda. It consists of seven Prapathakas (lessons). The first Prapathaka is introductory, the next three are structured in a question-answer style and discuss metaphysical questions relating to Atman (Self, Soul), while the fifth to seventh Prapathaka are supplements. However, several manuscripts discovered in different parts of India contain lesser number of Prapathakas, with a Telugu-language version showing just four. The common kernel of the Maitri Upanishad across different recensions, states Max Muller, is a reverence for soul, that can be summarized in a few words as, "(Man) is the Self – the immortal, the fearless, the Brahman". The Maitrayaniya Upanishad is notable for its references to theories also found in Buddhism, elements of the Samkhya and Yoga schools of Hinduism, as well as the Ashrama system. Srautasutras The Yajurveda had Shrautasutras and Grhyasutras attached to it, from fifteen schools: Apastamba, Agastya, Agniveshyaka, Baudhayana, Bharadvaja, Hiranyakeshi, Kaundinya, Kusidaka, Katyayana,