The Diagram is a text King Taravangian has created on various surfaces within his confines (i.e., ceilings, walls, floors, etc., due to his 'curse' given him by the Nightwatcher) during an unparalleled bout of his brilliance - twenty hours of lucid insanity that he didn't remember - which includes instructions for him on how to proceed toward uniting humankind on Roshar. This 'volume' is written in a language he devised, yet doesn't quite understand.
He'd written on it. Babbling the whole time, making connections no man ever made before, he had scribbled all over his walls, floor, even parts of the ceiling he could reach. Most of it had been written in an alien script - a language he himself had devised, for the scripts he had known had been unable to convey ideas precisely enough.
Adrotagia and her scholars had made notations throughout the document, offering theories on what various drawings and lists might mean, but still could make little sense of it.
The Diagram is not perfect; errors, or rather missed guesses ... for however educated, have been caught within it.
According to Taravangian, the Diagram warned that the personalities of the Radiants would introduce great uncertainty to the plans of those committed to it.
According to Brandon, followers of the Diagram have a similar origin as the Sons of Honor, but a different agenda.
"They will come you cannot stop their oaths look for those who survive when they should not that pattern will be your clue."
Coda of the Northwest Bottom Corner: Paragraph 3.
"One danger in deploying such a potent weapon will be the potential encouragement of those exploring the Nahel bond. Care must be taken to avoid placing these subjects in situations of powerful stress unless you accept the consequences of their potential Investiture."
"Q: For what essential must we strive? A: The essential of preservation, to shelter a seed of humanity through the coming storm. Q: What cost must we bear? A: The cost is irrelevant. Mankind must survive. Our burden is that of the species, and all other considerations are but dust by comparison."
Catechism of the Back of the Flowered Painting: Paragraph 1.
"You must become king. Of Everything."
Tenets of Instruction, Back of the Footboard: Paragraph 1.
"The Unmade are a deviation, a flair, a conundrum that may not be worth your time. You cannot help but think of them. They are fascinating. Many are mindless. Like the spren of human emotions, only much more nasty. I do believe a few can think, however."
Book of the 2nd Desk Drawer: Paragraph 14.
"There is one you will watch. Though all of them have some relevance to precognition, Moelach is one of the most powerful in this regard. His touch seeps into a soul as it breaks apart from the body, creating manifestations powered by the spark of death itself. But no, this is a distraction. Deviation. Kingship. We must discuss the nature of kingship."
Book of the 2nd Desk Drawer: Paragraph 15.
"Obviously they are fools The Desolation needs no usher It can and will sit where it wishes and the signs are obvious that the spren anticipate it doing so soon The Ancient of Stones must finally begin to crack It is a wonder that upon his will rested the prosperity and peace of a world for over four millennia"
A code that decrypts to: "Hold the secret that broke the Knights Radiant. You may need it to destroy the new orders when they return."
"But who is the wanderer, the wild piece, the one who makes no sense? I glimpse at his implications, and the world opens to me. I shy back. Impossible. Is it?"
West Wall Psalm of Wonders: Paragraph 8.
"(Note by Adrotagia: Could this refer to Mraize?)"
"One is almost certainly a traitor to the others."
Book of the 2nd Desk Drawer: Paragraph 27.
"Chaos in Alethkar is, of course, inevitable. Watch carefully, and do not let power in the kingdom solidify. The Blackthorn could become an ally or our greatest foe, depending on whether he takes the path of the warlord or not. If he seems likely to sue for peace, assassinate him expeditiously. The risk of competition is too great."
Writings upon the Bedstand Lamp: Paragraph 4.
"(Adrotagia’s 3rd translation from the original hieroglyphics.)"