Plutarch, De defectu oraculorum
Goodwin, Ed.

And when we offer victims before we come to the oracle, and crown them with garlands of flowers and pour wine on their heads, I see we do not any thing in all this that is absurd or repugnant to this opinion of ours. For the priests, who offer the sacrifices, and pour out the holy wine thereon, and observe their motions and tremblings, do this for no other reason besides that of learning whether they can receive an answer from the oracle. For the animal which is offered to the Gods must be pure, entire, and sound, both as to soul and body. Now it is not very hard to discover the marks of the body; and as to the soul, they make an experiment of it in setting meal before the bulls and presenting pease to the boars; for if they will not taste them, it is a certain sign they be not sound. As to goats, cold water is a trial for them; for if the beast does not seem to be moved and affected when the water is poured upon her, this is an evident sign that her soul is not right according to Nature. And supposing it should be granted that it is a certain and unquestionable sign that God will give an answer when the sacrifice thus drenched stirs, and that when it is otherwise he vouchsafes none, I do not sec herein any thing that disagrees with the account [p. 61] of oracles which I have given. For every natural virtue produceth the effect to which it is ordained better or worse, according as its season is more or less proper; and it is likely God gives us signs whereby we may know whether the opportunity be gone or not.