Isa Upanishad — The shortest of the principal Upanishads — eighteen verses on the Self that pervades all things, the paradox of knowledge and ignorance, and the golden door of the True.
Katha Upanishad — A dialogue between the boy Nachiketas and Yama, the god of Death, on the nature of the Self, immortality, and the path beyond death.
Kena Upanishad — A dialogue between teacher and pupil on the unknowable Brahman that powers every sense yet cannot itself be sensed, culminating in the parable of the gods and the straw.
Mandukya Upanishad — The shortest of the principal Upanishads — twelve verses on the syllable Om, the four states of consciousness, and the fourth state beyond waking, dreaming, and deep sleep.
Mundaka Upanishad — The Upanishad of the shaven-headed seekers — three Muṇḍakas on higher and lower knowledge, the two birds on the same tree, and the arrow of the Self aimed at Brahman.
Prasna Upanishad — Six seekers approach the sage Pippalāda with six fundamental questions about the origin of life, the nature of breath, the states of sleep and dream, the syllable Om, and the person of sixteen parts.