This is a fascinating book for those interested in Alchemy and Tantra. Leyenda makes the case that the famous Alchemist Thomas Vaughan and his wife Rebecca engaged in spiritual practices that clearly appear to be 'tantric' but, of course, Vaughan had no connection or influence to/from that tradition. It would appear he and his wife discovered them through their ardent love for each other.
This also suggest something I have felt for a long time: that the Rosarium Philosophorum was never just 'symbolic' but contains the seeds of sexual practices.
In any case, the work is scrupulously researched and well-written.