Lucan, in his "Pharsalia" (915-921), has enumerated some of the plants burned for the purpose of expelling serpents: "Beyond the farthest tents rich fires they build, That healthy medicinal odours yield, There foreign galbanum dissolving fries, And crackling flames from humble wallwort rise.

They get covered with a rank green scum, and if their inky depths be stirred, the foulest and most fearful odours issue forth.

I draw in the fresh air, odour-laden from orchard and wood.