Architraves of many pieces, and casting a vessel in a plaster box
Why a jointed architrave is stronger, and a recipe for a thin copper flask
The main note argues that an architrave built of several stones is stronger than one of a single block, provided the pieces are laid with their length toward the centre of the earth, since stone's grain (nervo) runs crosswise, unlike the grain of plants. A drawing shows a composition of stone blocks of various forms, with a small circle sketched at the left. Along the right margin, three figures and a detailed recipe describe how to build a vessel or bottle enclosed in a box: coating a clay core, working it in building plaster soaked with glue, gilding and burnishing, and using the form to take an impression in thin copper, baked until porous.
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An architrave of many pieces versus one
An architrave made of several pieces is stronger than one of a single piece, provided the pieces are set with their lengths turned toward the centre of the world. The reasoning turns on the direction of the stone's grain.
The grain (nervo) of stone runs crosswise
Leonardo explains that stones have their nerve or grain formed crosswise, toward the opposite horizons of one and the same hemisphere. This is the contrary of the grain of plants, and it is why the jointed architrave carries load better.
Casting a thin copper vessel in a plaster form
Three figures show a flask and a bottle enclosed in a box. The recipe coats a clay core, cuts it with a diamond compass, works it in building plaster soaked with glue, then gilds and burnishes it; the same material, well dried and glued, takes a good impression of thin copper (Venere). The plaster is stiffened with chopped cloth and lime and baked until porous.