She had no need for tools like my master did. With the air of a master who could see an
error of a single micron in the grinding of a telescope's mirrors with the naked eye, she
continued to trace various parts of the body with her finger.
After a while, she spoke again.
"Ah, seems I was mistaken. This is definitely my work."

The Case Files of Lord El-Melloi II, Volume 3, Chapter 3, Part 2