Tailor's Chalk: Thin Soapstone Cakes with Bevelled Edges

Tailor's chalk, also called French chalk, marks cloth for cutting and brushes off again; today it is usually talc. Soapstone is mostly talc, soft and easy to work, and seamstresses have long marked with it. Saw a block into thin square cakes and bevel the edges so they draw a fine line. The picture: our diagram, a cake from above and from the side, and the line it leaves on cloth.