Apuleius’ Testimony on Initiation into the Eleusinian Mysteries

I approached the confines of death: and having trodden on the threshold of Proserpina returned, having been carried through all the elements. In the depths of midnight I saw the sun glittering with a splendid light, together with the infernal and supernal gods: and to these divinities approaching near, I paid the tribute of devout adoration.

Generation of the Soul

The soul descends Corically [or after the manner of Proserpine] into generation, but is distributed into generation Dionysiacally,  and she is bound in body Prometheiacally  and Titanically: she frees herself therefore from its bonds by exercising the strength of Hercules; but she is collected into one through the assistance of Apollo and the savior Minerva, by philosophical discipline of mind and heart purifying the nature. – Olympiodorus

Orphic Mysteries

What Orpheus delivered in hidden allegories, Pythagoras learned when he was initiated into the Orphic Mysteries; and Plato next received a perfect knowledge of them from the Orphean and Pythagorean writings. – Proclus

Initiation into the Eleusinian Mysteries

The perfective rite [τελετη, telete] precedes in order the initiation [μυησις, muesis], and initiation, the final apocalypse, epopteia.” – Proclus

Προηγειται γαρ, ἡ μεν τελετη της μυσεως, αυτη δε της εποπτειας.