Tod Cutler Arrows vs Leather Armor

The video is interesting, but what really caught my attention was the top comment, which claims to quote a recipe for cuir bouilli from a text kept at the Ashmolean museum:

"Take lether that ys half tannyd and drye hym, and schave the flesshe syd; and take glwe wt water, and set yt over the fyere, and melte yt wt water, and then al hote ly yt a pone the leder on the flesshe syde, and strawe ther on the powder of glasce bete yn a brasene morter wt fylyne of yrene y mellyd to geder; and then laye a nother pece of the same lether flesshe seyde to flesshe, and nayle hym to the scylde and lete hyme drye, and ther nother sper nother ege tole enter ther ynne"

As far as I can translate into more modern English, it'd say something like this:

"Take leather that is half tanned and dry it, and shave the flesh side; and take glue with water, and set it over the fire, and melt it with water, and then all hot lay it upon the leather on the flesh side, and strew thereon the powder of glass beaten in a brazen mortar with (filling?) of (urine?) all melded together; and then lay another piece of the same leather flesh side to flesh, and nail it to the shield and let it dry, and there neither spear nor edge shall enter therein."

I can't corroborate the authenticity of the quote, or figure out exactly where it's from, but it's pretty interesting nonetheless. If true, the powdered glass mixed with glue in between two pieces of partially tanned leather sounds something like rudimentary fiberglass. Also, half tanned leather would be closer to rawhide, which would probably be a lot better than leather as armor.