Inventor notebooks are essential to your work. Here is what wikipedia says: “An inventor’s notebook is used by inventors, scientists and engineers to record their ideas, invention process, experimental tests and results and observations. It is not a legal document but is valuable, if properly organized and maintained, since it can help establish dates of conception and reduction to practice. It may be considered as grey literature. The information can improve the outcome of a patent.”

Here is a typical entry. This is a page from Alexander Graham Bell’s notebook dated March 10, 1876!