Srimad Bhagvata Mahapurana: Book 4: Chapter 18: Verses 1-18
King Prthu milks goddess Earth in the form of a cow
Maitreya continued : It was thus that goddess Earth glorified Prthu, whose lips were quivering through anger. She was frightened: but she made herself quite and steady with an effort of her will and spoke again:-- "O Lord You possess power to do anything that You please; kindly control Your wrath and consider what I tell You (in humble submission). Like the bee, a wise man takes the essence from everything. Sages who have realized the Truth have discovered and tested methods for the realization of human ends here as well
as hereafter. Anyone of the later times who follows with faith and reverence those expedients found and taught by the ancient masters easily achieves the purposes of his life. He who in his foolishness disregards them and undertakes to accomplish (ignorantly planned) purposes in his own (vainly independent) ways, can never be successful in his efforts. His ends are never realized, even though his efforts are renewed every now and then. O king ! I noticed that the herbs and annual plants that had been evolved of old by Brahma, the Creative Agent of God, were being used and enjoyed by those who were unrighteous and had not undertaken any religious vows and observances. I (therefore) absorbed (into my bosom) the herbs and annual plants, finding myself unprotected and uncared for by Your predecessors and that a generation of thievish people flourished on earth. I meant to preserve them for sacrificial rites. It is natural that the plants have got assimilated in me through a long process of time. Now You are the person competent to draw them forth by some expedient known to be effective in this behalf. O Hero of mighty arms, 0 Lord sustaining the life of beings, pray, find a calf, a befitting milk-pot and one who can draw the milk, so that, full of affection for the calf, I shall yield for you the desired objects in the form of milk if you want to have nutritious food coveted by living beings. O king of boundless power ! remove my ruggedness and make me level so that, even when the rains have passed, the water poured down by the god of rain may stand on me. May all be well with You!"
Accepting this agreeable and wholesome advice of goddess Earth, the Emperor made a calf of Swayambhuva Manu and drew from her in his own hands all species of herbs and annual plants. Likewise all other wise and intelligent persons too take the essence of everything and so after Prthu others also drew from Earth, as a cow tamed by him, the objects sought after by them . The seers and sages, 0 most righteous one, made a calf of Brhaspati (the preceptor of the gods), milked the goddess and got the sacred Veda for milk, their milk-pots being the organs of hearing and of speech and the mind, which is the sense of senses. The gods made a calf of lndra (their king) and drew (from Earth) the (ambrosial) drink known as Soma besides mental vigour, ardour of the senses and physical strength for their milk in a vessel of gold. The Daityas and Danavas made a calf of Prahrada, the noblest of them all, and obtained wines and distillates (toddy etc.) for their milk in a bucket of iron. The Gandharvas (celestial musicians) and Apsaras (heavenly nymphs) made a calf of Viswavasu and derived the sweetness of song and beauty for their milk in a cup of lotus. The venerable Pitrs-the deities presiding over the rites in honour of the spirits of departed ancestors-made a calf of Aryama (one of the twelve deities presiding over the sun, the chief of the Pitrs) and drew with reverence what is known as Kavya (food for the Pitrs), which they held in a sun-dried earthen vessel and which was milk for them.