- "Let's see.. is mass equals i times z, and E equals the square root of z times c squared, and the flux dispersal rate is inversely proportional to the fourth root of n.. carry the nine, then.."
- —Doc reads out of his notebook.
Doc's notebook was a book for writing in, which was possessed by Emmett Brown.
The notebook documented thirty years of scientific breakthroughs in building a working time machine. Doc referred to it when the DeLorean time machine did not reappear one minute after temporal displacement. He noted that if the book fell into the wrong hands, the effects could be catastrophic.
Inside the notebook were schematic diagrams, circuit diagrams, equations, and notes to himself, particularly for October 26, 1985, in which he had to wear a bulletproof vest, walk Einstein before the time experiment, check the time circuits for stickiness, and remind Marty to bring a camera — i.e. the JVC camcorder.
In 1986B, the notebook was nearly blank, due to the ripple effects catching up with it. The picture of the flux capacitor, however, was still intact on one page and inspired Citizen Brown enough to be able to repair the DeLorean.