Being Sent From Pillar to Post

There was that strange Scottish blanket in The Comfortable Arts that mystified me because its construction was supposed to reflect twill as done on warp-weighted looms, and I couldn't figure out how a warp-weighted loom could produce twill since I've only seen photos of such looms set up for tabby weave, with one heddle rod.

I'd hoped that Keep Me Warm One Night by the same author would have more information, since it covers the same ground, Canadian textile history, with a lot more text.  What I got was much the same information with a reference to see Hartmann's The Warp-weighted Loom for an explanation.  This is rather dispiriting news.  I finally finished reading that book not too long ago after taking an uncharacteristically long time to get through to the end, and I completely missed whatever it was I should have noticed.

The content of The Warp-weighted Loom is great, if you allow for frequent instances where the author gets into abstruse discussions about researchers' interpretations of historical data and the probabilities of those interpretations being correct.  Commendable, necessary, and exhaustive.  These are punctuated with a high level of technical detail I can only hope makes sense to experienced weavers and archaeologists.  There's a great deal of material in the book and there's little white space on the page around the type, a combination that makes for tough going.  Normally, it is my particular joy to search through a wealth of written information and pull out the pertinent parts.  Right now, I'm out of sorts and don't feel up to the endeavour, so I'm putting it off.

I found this tantalizing quote in Kay Wilson's A History of Textiles under the heading float weaves:

The opposite to the weft-faced twill is the steep or warp-faced variety.  The angle of the wale is more than forty-five degrees, and there are more warp than weft.  Denim and gabardine are modern examples; they show weaving sequences of under tw [sic], over one.  If the warp and weft counts are about equal, and the weft goes under two, over two warp, an even-sided (and reversible) twill is produced.  These were woven on the warp-weighted looms of Bronze Age Europe.  The even-sided twill allowed for an even division of the warp between the front and the back of the fixed shed rod.

Reading this passage, I sort of get it but I don't.  The author does not make explicit the difference between 2/2 twill and the tabby structure basketweave.  Pity this weave doesn't rate an illustration in the book.

Fortunately, Katherine Larson's The Woven Coverlets of Norway does contain an illustration of balanced 2/2 twill weave structure.

I'm still unclear about how many heddle rods are required for twill, where the rods sit on the warp-weighted loom, and how you work them.  Not that plain tabby wouldn't be challenge enough, had I the loom to play with, but I'd like to know.  I understand that warp threads for the rosepath pattern are picked up manually.