"The recommended pen hold" is taken from a 1553 manuscript and it represents the earliest indexing tool. Early versions of Indexes, as a means of organization, predate the printing press and were hand-written early on.

Pliny the Elder, wrote his Naturalis Historia (Of Natural History) in the first century and dedicated the first of its thirty-seven books to serve as huge table of contents listing each of the other books and the subjects discussed. This could be considered as an early experiment in indexing.

Hans H. Wellisch has written an fascinating article on the history of indexes which some of you may find to be of interest. The oldest printed indexes.pdf

By the mid-twentieth century, indexers were using what is known as the shoebox method for indexing. It is so named because indexers, using typewriters, would type out entries on 3 x 5 cards and then organize the cards in shoeboxes. A shoebox is the perfect size to keep the cards neat and tidy and, once all of the entries had been written, the indexer then would type all of the entries listed on the cards to create the index. Using this method, indexers had to alphabetize, input entries, and format the index manually. That process was just as time-consuming and tedious as it sounds but it was used by professional indexers until indexing software programs were developed and available for purchase.