Though writing in the margins of text is an ancient tradition, it
was discussed and studied at the beginning of the modern age.
Treatises on "the art of studying" advise readers to make comments on the text throughout their reading. The purpose of these notes is to allow the reader to focus his or her attention, help remember details, and make subsequent reading of the book easier. The most common markings included underlining, crosses, arrows and pointing hands, also known as manicules. The use of these "ghost notes" is a controversial reading method; although authors from ancient times approved of their usage, some practices such as thumbnail markings or cornered pages were deemed utterly unacceptable of worthy readers. It was thought that readers should limit themselves to adding a few words in the margin to follow the text. On the other hand, some wordy readers would have blank pages inserted between the printed ones to increase their note-taking space.
On a page inserted in a New Testament from 1538, the reader laid out five columns of various biblical citations about children, milk, seeds and choices. This table illustrates the scholarly practice of creating collections of "common places". It also demonstrates an essential principle of biblical study, the self-explanation of Holy Scripture. Through cross-referencing, each text made the other easier to understand.