Laṅkāvatāra Sūtra
The later "Laṅkāvatāra Sūtra" presents the "tathāgatagarbha" as being a teaching completely consistent with and identical to emptiness. It synthesizes "tathāgatagarbha" with the emptiness ("śūnyatā") of the "prajñāpāramitā" sutras. Emptiness is the thought-transcending realm of non-duality and unconditionedness: complete freedom from all constriction and limitation.