Piece goods manual : Fabrics described; textile, knit goods, weaving terms, etc., explained ; with notes on the classification of samples (1917)
Blanco, A. E · Shanghai : Statistical department of the Inspectorate general of customs · leaf 21
Figure 5. TWO-AND-TWO TWILL WEAVE. This figure illustrates a four-end, two-warp and two-weft, regular twill. Neither warp nor weft predominates on the surface. This style of twill is known as Harvard twill.
Textile fabrics
Internet Archive · Claire T. Carney Library, University of Massachusetts Dartmouth · Public domain (published before 1931). Free to use for anything.