Smith's Work Furnace of Rammed Clay With a Bellows Hole Through a Wooden Back (Theophilus, 12th Century)

"Near the wall, by the window, on the left side of the person sitting, a piece of wood is fixed in the ground."

Fix a piece of wood firmly in the ground near the wall, three feet long and scarcely two fingers thick, with a finger-size hole through it four fingers above the ground. Peg on in front a straight piece four fingers wide and as long. In front of this fasten another of equal breadth and length so there is a space of four fingers between them, held outside by two or three stakes.

Take clay newly dug, not beaten nor mixed with water, put a little into the space and ram it hard with a rounded piece of wood, then more, until two parts of the space are filled and the third left empty. Take away the front wood, cut the clay level in front and on top with a long knife, and beat it hard with a thin piece of wood.

Beat clay mixed with horse dung and make the furnace and its hearth, covering the wall so the fire cannot burn it. Pierce the clay with a slender stick through the hole in the back wood, for the bellows tube.

Put the bellows tube in the hole, lay fire and charcoal at the back and front, and blow to dry the furnace.

From Theophilus, **De Diversis Artibus**, Book III, chapter III, translated by Robert Hendrie (1847) (checked on the archive.org scan essayuponvarious00hend, p. 211). The finger-to-centimetre figures, the tools and the diagram are ours.