Eph's paper on strings [Early Music Oct 1976 pp430-437] has the Ganassi picture from  and a bit of Mary Burwells' remarks in 4th Chap of her lute tutor p.7 [transcriptioon by Thurston Dart, Galpin Soc Journal XI, (1958) p.3

The le Roy is from p 47 of Vol1 of my CNRS

Check that there isn't more in Capirola. I seem to remember a version including the idea of "twitching" the string. Is this in Mersenne? And counting the number of "threads" in the string and matching them.

Silvestro Ganassi: Lettione Secunda pur della prattica di sonare il violone d'arco da tasti (1543) Facs. Forni

Marin Mersenne, Harmonie Universelle (1635) transl. Robert E. Chapman (1957) p.79