The 21st diagram (Figura Divina) of the first part of the book

The Secret Symbols of the Rosicrucians of the 16th and 17th Centuries is a book published by the Rosicrucian Order, edited by H. Spencer Lewis. It contains (among others) reproductions of Rosicrucian charts and symbols from the above era.

The 21st diagram of the first part of the book (seen to the right) visibly served as an inspiration for the Plane chart, a diagram describing the hierarchy of the mazoku in the worlds created by the Lord of Nightmares. Two symbols in particular, the one in the middle between the words "SEPARATIO" and "NON SEPARATIO" and the one to the lower left, under the handwritten text "Sulphur philosophorum" look like the original versions of the seals of Death Fog and Chaotic Blue, respectively.

On the 12th diagram of the first book (left), two hands can be seen reaching out from the clouds, which bear great resemblance to the ones seen on Dark Star Dugradigdu's detailed symbol (below).