The Henry Tiffin commonplace book is a commonplace book that was kept by Tiffin from 1748 to 1776. The contents of the book are not chronological and include a collection of narratives, including a lengthy one on his voyage aboard the East Indiaman Eagle to India in 1774, poems, songs, treatise on navigation, and a number of watercolors of ships and places. Tiffin also includes comments about a voyage on board the HMS Tavistock from 1748 to 1749 to the West Indies, and voyages on board the Royal Duke in 1752 from the Straits of Malacca to China, as well as voyages to Halifax, Nova Scotia, and from Jamaica to Boston.

One example of the detailed contents includes "A [Succinct] List of the Royal Navy for 1774," in which Tiffin presumably names all of the vessels, including types and armament, from first rates down to sloops of ten guns in the Royal Navy of the period. He also lists all of the places to which he has sailed. There are essays on "Cruelty and Lust," an " Elegy to a Lady," and a long epistle on the death of General Wolfe at Quebec in 1859, in addition to essays on geometry, trigonometry, astronomy, and navigation. The book has numerous watercolor illustrations throughout. For a detailed appendix of these illustrations, see the collection register at the front of the box.