Your majesty says very true: if your
majesties is remembered of it, the Welshmen
did good service in a garden where leeks did
grow, wearing leeks in their Monmouth caps;
~ William Shakespeare, Henry V, Scene VII
One (believed) extant example of a Monmouth cap was described in detail by Kirstie Buckland in Costume. It is described as being knit with a 2-ply wool with approx. 2 stitches per inch, dyed a dark brown after or during felting. Knit in the round, all in stocking stitch, it has a double brim knit together at the edge, a loop, and a small ‘button’ at the top. It is helmet-shaped, and knit using ‘multiples of ten and twenty’.
I tried to find a modern yarn that best matched the description above, and settled on Cascade Lana Grande – a two-ply, 100% wool yarn, with a gauge of 2 stitches per inch. I chose a natural/off-white colour. I will use black walnut dye to get it a dark brown (I hope). I’m knitting it large and hoping it will felt up.