Haven't seen that one, I think (sometimes a bit confusing, all these titles with prayers and graves)
I like Mulargia, so I think I go looking for a copy.
I was in Inverness a couple of years ago, and discovered that a professor from Edinbrough gave a few summer lectures in the local library. One was dedicated to Bonny Prince Charlie, the second to William Wallace. Very interesting; turned a few rainy afternoons into real events. We discussed Braveheart and the ius primae noctis, and read a few texts on the subject. He too thought it had a historical base (I remember he said, laconically: I would be surprised if such a thing never occured in history. So would I)