As per Vedas, the Rahasyas are mentioned in the same breath as other sacred scriptures like Itihasas, Puranas and Vedas.
"In this way all the Vedas are manifested along with the kalpas,rahasyas, Brahmanas, Upanishads, Itihas, anvakhyatas and the puranas." - Gopatha Brahman purva 2:10.
Is this a reference to Tantras (many are titled "Rahasya")? Or to scriptures like Shiva Rahasya, Preta Manjari, Dattatreya's Tripura Rahasya and Avadhoot Gita which are part of extended Tantric tradition?