1847 Calligraphic Ink and Graphite Drawing with Swans and Floating Eye, Plus Two Accompanying Love Letters

This I found in New Hampshire this week, and it is not just the sort of thing I love, but also the sort of thing that provokes a sense of responsibility in me to be its steward. The curious drawing itself, ink and graphite, appears to have been done on paper that was folded into a letter--and though I haven't removed it from the frame I'd be willing to bet it matches that of the two love letters tucked into a pocket on the back of the frame. Those letters are dated 1847 and were written from a Morgan W. Brown to an Emily Hedenberg in St. Louis, MO ("and nobody else!"), who writes of kissing her miniature (I presume a miniature painting of her) which he also describes showing to a number of his relations to great approval. ("Time and space does only add to the veneration I hold my dear to you and you alone… if I should have the misfortune to sink to the bottom of a lake or river before I see thee again, remember that the king and your miniature go with me…") He describes his travels fro