The triangle is the triune of mind/body/soul and relates to the philosophers stone. The unicorn dipping its horn in the fountain purifies the water. And you'll never guess what that means. The 3 becomes 2, and the two become one.

It may be slightly off the given path but what was the story regarding a female attending the last supper ? Because I found in that same library of images 2 separate images of a female sitting at the table during the last supper . One image her being on the right side and the other image being on the left side . Now since they are from religious texts and what ever was said to deny it being the case .