From the Kuenstlich und Fuertrefflichs Kochbuch again:
9 Almond Milk
Item take almond kernels and blanch them in boiling water. Pound them small in a mortar and pour on a little rosewater so that they can be pounded. When they are small, take the out and place them in a clean grinding vessel (rein scherben) and grind them as small as possible. Take them out onto a nice cloth and pass it through with rosewater that is cold. Grind it again and pass it through again, thus they turn thick like a thick milk. That will be good almond milk.
17 Almond Milk that does not Curdle in a Soup
Item take rosewater, salt it like a soup, and when it has boiled, put it away and let it cool. Pass it through and prepare it like other almond milk. Thus it does not curdle.
Almond milk is ubiquitous in our recipe collections, but it should probably be said first of all that it was never common. Almonds and rosewater were luxury foods only available to the wealthy, and most people made do without milk on fast days. We have a few detailed descriptions of how to produce it, and this one is neither unusual nor terribly useful. The second recipe, though, is interesting. We know from contemporary recipes that almond milk could be made to curdle, but when it was cooked, that was not necessarily what you wanted to happen. I do not know whether pre-salting and boiling rosewater will actually do anything, but the author clearly thought so. It might be worth trying out.
The short Kuenstlichs und Fuertrefflichs Kochbuch was first printed in Augsburg in 1559 and reprinted in Nuremberg in 1560 and subsequently. Despite its brevity, it is interesting especially as it contains many recipes for küchlein, baked or deep-fried confections, that apparently played a significant role in displaying status. We do not know who the famous cook referenced in the title may have been or if he ever existed.