narayanah-named Narayana; sah-that; bhagavan-Supreme Personality of Godhead, Maha-Visnu; apah-water; tasmat-from that; sanatanat-eternal person; avirasit-has sprung; karana-arnah-the Causal Ocean; nidhih-expanse of water; saṅkarsana-atmakah-the subjective portion of Saṅkarsana; yoga-nidram gatah-in the state of deep sleep; tasmin-in that (water); sahasra-amsah-with thousands of portions; svayam-Himself; mahan-the Supreme Person.
The same Maha-Visnu is spoken of by the name of "Narayana" in this mundane world. From that eternal person has sprung the vast expanse of water of the spiritual Causal Ocean. The subjective portion of Saṅkarsana who abides in paravyoma, the above supreme purusa with thousands of subjective portions, reposes in the state of divine sleep [yoga-nidra] in the waters of the spiritual Causal Ocean.
Yoga-nidra (divine sleep) is spoken of as ecstatic trance which is of the nature of the bliss of the true subjective personality. The above-mentioned Ramadevi is yoga-nidra in the form of Yogamaya.