Make, learn and talk about needle lace.
In the process of doing the documentation for a piece of reticello lace for the Society for Creative Anachronism I came across two Sienese school paintings from the first half of the fourteenth century that appear to depict drawn thread laces. The second is the pillow on which the allegorical figure of Peace is reclining in Ambrogio Lorenzetti's Allegory of Good Government in the Palazzo Publico, Siena (1337), which combines square drawn thread motifs with whitework embroidery and looks very much like Hardanger work, and the other is a row of what looks like ornamental hemstitching on Simone Martini's Dream of St. Martin in Assissi. Both items are domestic linens and not notably opulent. I did not come across anything in a fairly extensive literature search that was as old as this and reasonably plausible.
The project that I made for the SCA was a turban pieced together from three short strips of linen, which I sewed together using a flat felled seam using an ornamental hemstitch on the felling, which produced something that looked like a narrow lace insertion next to the seam. Looking at Saint Martin's sheet I am thinking that may be the sewing technique there.