Every serious practice in history has kept notes, and almost every one of them has had a slightly self-important name for the notebook.
Naturalists kept field journals. Chemists kept lab books. Sailors kept logs, cooks kept receipt books, and engineers kept the sort of grid-lined notebooks that are still, quietly, the best-designed object in most offices. The names differ. The function does not: write it down at the time, because you will not remember why it mattered, and because the person who benefits most from your notes is you in four years.
A grimoire is that. The word is chosen with a straight face and a slight smile. It is not a spellbook, there is nothing to consecrate, and no one is going to check the binding.
What goes in it
- What you tried, and what actually happened, including the parts that make you look foolish. Especially those.
- Measurements, settings, quantities, temperatures, part numbers. The boring specifics that are impossible to reconstruct later.
- Diagrams. Bad ones are fine. The act of drawing a system is a test of whether you understand it, and it is a test you can fail privately.
- Sources: what you read, who told you, and how much you believed them at the time.
- Connections — the moment when something in one field suddenly explains something in another. These are the entries you will reread.
- Open questions. A running list of things you do not understand yet is worth more than a list of things you have finished.
Physical or digital
Both work. Paper is better for thinking, drawing and remembering; it is unsearchable and it burns. Digital is searchable, backed up and instantly retrievable; it also quietly encourages collecting rather than processing, which is not the same activity and feels far too similar.
Most people who keep one properly end up with a hybrid: a paper notebook for the working-out, and something searchable for anything that turned out to be worth keeping. The system matters much less than the habit, and anyone who has spent more than a fortnight choosing the system has found an extremely comfortable way of not starting.
The one rule
Record the failures with the same care as the successes. A notebook containing only things that worked is a portfolio, and portfolios teach nobody anything — least of all their author. The value of the whole practice is in the record of what did not work, kept honestly enough that it is still useful when you have forgotten how sure you were.