Lib. IX.
Lib. IX appears to be a plate-numbered section of a scientific or technical treatise, its record giving no author, date or place, so the pictures are the only evidence. Engraved plates show well-drawn mechanical tools with hooks and screws, vaulted masonry chambers, a planetary orbit diagram, and a fine ruled grid, all in plain black linework on pale paper. A designer could take from them a precise, diagrammatic line style with clean labelled figures and a restrained grid-based layout.
