Sometimes I think architects have the best notebooks. This one, from architect Lebbeus Woods, is certainly a great example:

In the architect’s own words:

For a period of ten years, a part of my practice was carried on in a space of ten by fifteen by two centimeters—one might call it an extreme space. Beginning in 1991, I was traveling very much—lecturing, teaching, and working on the occasional project—and not often near my drawing board. As a way of coping with being on airplanes, trains, living in hotel rooms, cafes, and bars, I began to keep notebooks in which I could draw and write while on the move. This was very important to me, as my thoughts were alive with new ideas that could not be put on hold. So the pages of the notebooks became a studio I could keep in my pocket, unfolding its nearly limitless space whenever I needed….
Notebooks are portable. They can be kept secret, or published. Technically, they are simple to make. Pen and paper. The hand, eye, and thought. Freed from any sort of burdensome apparatus, thought becomes more agile in confronting itself.