Matsyapurana 142.39

142.39

kramāgataṃ mayāpyetat tubhyaṃ noktaṃ yugadvayam
ṛṣivaṃśaprasaṅgena vyākulatvāttathā kramāt //

Now I shall tell you the creation of Tretâ Dvâpara and Kaliyuga I told you before about Satyayuga and part of Tretâyuga I did not tell you anything about the remaining portion of Tretayuga, Dvâpara and Kaliyuga on account of my having been engaged in the narration of the generations of the Ṛiṣis I, therefore, tell you, now, about the Tretâyuga that was left unsaid There was Manu in the beginning of the Tretâ age and the then Ṛiṣis dictated Śrauta and Smârta dharma by the light thrown on them by Brahmâ They wrote on marriage, Agnihotra, and other Śrauta dharmas according to the Ṛik, Yajuḥ, and Sâma Vedas They also gave out the injunctions of the Smṛitis, truthfulness, Brahmacharya (celibacy), Varnâśrama and other Achâra dharmas.—38 43 and perceived in their hearts, by thinking about them once only. In the beginning of the first Kalpa, those mantras (or laws of the Universe) arose of themselves in the minds of the Devas in testimony whereof those who are Siddhas (perfect) and others also can have the knowledge of the Mantras. In the past Kalpa there were one hundred thousand mantra yogas, by the power of the sages even those who follow them, can realise them, and those mantras now lie hidden in the Pratimas or images of the Devas.—44-46.