Two-page specification of an English patent dated March 25, 1797, granted to Joseph Barton, a London chemist, for an improved method of preparing indigo for dyeing wool, silk, linen, cotton and other goods, and for giving blue shades to linens, woollens and papers. The text explains that quantities cannot be fixed because indigo varies in quality. It describes grinding the indigo finely, dissolving it in acid or alkaline solvents, adding tin, iron, zinc or alum as a fixing base, and neutralizing excess solvent so the colour stays durable and bright.

US design patent No. 34,119, granted February 19, 1901 to John Thomas Baron of Providence, Rhode Island, assignor to Farnsworth, Hoyt & Company of Boston. It covers an ornamental design for a woven fabric, intended especially for a duck used to lining shoes and other articles subject to hard wear. The design shows interwoven curved tapes or ribbons that intersect at irregular angles, with square intersections at intervals. The patent has a drawing page and a one-page specification with a single claim.