esoteric writings; Upanishad
Refers to sacred Hindu treatises (Upanishads) or, more broadly, writings containing secret or profound teachings. The Upanishad sense is domain-specific.
Reading the Upanishads of Indian philosophy is difficult.
He studied esoteric writings and sought the meaning of life.
奥義 (profound meaning) + 書 (writing). The term is used to translate the Sanskrit 'Upanishad'.