At yesterday’s TeX meetup in Ladenburg—curiously enough, the Heidelberg TeX meetup has been taking place in my neighboring town for several years now—I was shown a beautiful, old Latin grammar book. What was particularly nice about it was the index. Next to the page numbers were small superscript numbers indicating whether the corresponding index entry was located in the first, second, third, or fourth quarter of the page. This actually makes it easier to search the page. When you consider that 100 years ago the entire index was still compiled by hand, you can imagine what a labor-intensive task that was.