The Odyssey by Homer Book 10 Page 34

Moreover you must offer many prayers to the poor feeble ghosts, and promise them that when you get back to Ithaca you will sacrifice a barren heifer to them, the best you have, and will load the pyre with good things. More particularly you must promise that Teiresias shall have a black sheep all to himself, the finest in all your flocks.

“‘When you shall have thus besought the ghosts with your prayers, offer them a ram and a black ewe, bending their heads towards Erebus; but yourself turn away from them as though you would make towards the river. On this, many dead men’s ghosts will come to you, and you must tell your men to skin the two sheep that you have just killed, and offer them as a burnt sacrifice with prayers to Hades and to Proserpine. Then draw your sword and sit there, so as to prevent any