In former times, when they had fewer opportunities of selling it, they used to gather the frankincense only once a year; but at the present day, as there is a much greater demand for it, there is a second crop as well. The first, and what we may call the natural, vintage, takes place about the rising of the Dog-star, a period when the heat is most intense; on which occasion they cut the tree where the bark appears to be the fullest of juice, and extremely thin, from being distended to the greatest extent. The incision thus made is gradually extended, but nothing is removed; the consequence of which is, that an unctuous foam oozes forth, which gradually coagulates and thickens. When the nature of the locality requires it, this juice is received upon mats of palm-leaves, though in some places the space around the tree is made hard by being well rammed down for the purpose. The frankincense that is gathered after the former method, is in the purest state, though that which falls on the ground is the heaviest in weight: that which adheres to the tree is pared off with an iron instrument, which accounts for its being found mingled with pieces of bark.

– Pliny the Elder

Frankincense, terebinth, and Italian bergamot.