In ancient Egyptian ritual manuals you often find comments made either by the authors themselves or by later readers. These comments could refer to a specific content, like adding what a different manuscript said. They could also assess the quality of a ritual.
In one of the most extensive ancient Egyptian => magical papyrus scrolls the author compiled several vessel and lamp divinations from various sources and judged their individual efficacy. At one point he writes:
I say that this vessel inquiry of the lamp is more beautiful than the first one.
This tells us something unique about the author: He didn’t only write the ritual instructions down to preserve them. He actually practiced them. And based on his practical experience he included comments.
This shows us that the most extensive ancient magical manual preserved today is not a copy of an existing book, but instead it is a compilation of rituals and information relevant to ritual practice that was gathered by the author over a period of time. The content of the scroll is based of the individual preferences and practical experiences its author made. And as such the scroll reflects the highly individual interests and the professional development of a ritual practitioner over 1.700 years ago in the ancient city of Thebes.