"It was an article in the Druids' creed, and one to which they strictly adhered, that no temple with a covered roof was to be built in honor of the gods. All the places appointed for public worship were in the open air, and generally on some eminence from which the moon and stars might be observed; for to the heavenly bodies much adoration was offered. But to afford shelter from wind or rain, and also to ensure privacy and shut out all external objects, the place fixed upon, either for teaching their disciples or for carrying out the rites of their idolatrous worship, was in the recess of some grove or wood. An oak-grove was supposed to be the favorite of the gods whom they ignorantly worshiped, and therefore the Druids declared the oak to be a sacred tree. The Druid priest always bound a wreath of oak-leaves on his forehead before he would perform any religious ceremony. One of these ceremonies was to go in search of the mistletoe, which sometimes grows on the oak and was considered as sacred as the tree itself, being much used in their worship. One priest would climb to the branch on which the misletoe was growing and cut it with a golden knife, while another priest stood below and held out his white robe to receive it.