Regarding them, scholar Thomas Hartwell Horne explains: “They . . . reckoned which is the middle letter of the Pentateuch [the first five books of the Bible], which is the middle clause of each book, and how many times each letter of the [Hebrew] alphabet occurs in all the Hebrew Scriptures.”3
A Book for All People. 1997. p. 7
3. An Introduction to the Critical Study and Knowledge of the Holy Scriptures, by Thomas Hartwell Horne, 1856, Vol. I, p. 201.
A Book for All People. 1997. p. 31