Plutarch, De Iside et Osiride
Goodwin, Ed.

This then is that account of these things which best suits the nature of the Gods. And if I now must, according to my promise, say something concerning those things they daily offer by way of incense, you are in the first place to understand this, that these people make the greatest account imaginable of all endeavors that relate to health; and more especially in their sacrifices, purgations, and diets, health is no less respected than devotion. For they think it would be an unseemly thing to wait upon that nature that is pure and every way unblemished and untouched, with crazy and diseased minds or bodies. Whereas, therefore, the air that we most use and live in hath not always the same disposition and temperament, but in the night-time grows condense, compresses the body, and contracts the mind into a kind of melancholy and thoughtful habit, it becoming then as it were foggy and dozed, they therefore, as soon as they are up in the morning, burn rosin about them, refreshing and clearing the air by its scattered particles, and fanning up the native spirit of the body, which is now grown languid and dull; this sort of scent having something in it that is very impetuous [p. 137] and striking. And perceiving again at noon-time that the sun hath drawn up by violence a copious and gross exhalation out of the earth, they by censing mix myrrh also with the air; for heat dissolves and dissipates that puddled and slimy vapor which at that time gathers together in the ambient air. And physicians are also found to help pestilential diseases by making great blazes to rarefy the air; but it would be much better rarefied, if they would burn sweet-scented woods, such as cypress, juniper, and pine. And therefore Acron the physician is said to have gained a mighty reputation at Athens, in the time of the great plague, by ordering people to make fires near to the sick; for not a few were benefited by it. Aristotle likewise saith that the odoriferous exhalations of perfumes, flowers, and sweet meadows are no less conducing to health than to pleasure; for that their warmth and delicacy of motion gently relax the brain, which is of its own nature cold and clammy. And if it be true that the Egyptians in their language call myrrh bal, and that the most proper signification of that word is scattering away idle talk, this also adds some testimony to our account of the reason why they burn it.