From Thomas Jefferson Encyclopedia
There are many interesting clothing items in the Monticello collection that belonged to Thomas Jefferson and other family members. One of the most interesting is a red silk under waistcoat  believed to have been Jefferson's.
Under waistcoats were worn by men of all economic status as a middle layer of clothing during the late eighteenth and nineteenth centuries. They were worn on top of shirts and were designed to be seen peeking out from underneath an outer primary waistcoat. However, this particular Jefferson under waistcoat is very different from most others.
Just as Jefferson built and then later altered his home Monticello "with a greater eye to convenience," he also modified some of his clothing to meet his changing needs. Jefferson's red under waistcoat was altered by the addition of a lining consisting of opened or flattened stockings sewn into the interior to make the garment warmer. Since the stockings were embroidered with "TI" stitched over "9.7.," we know they were one of Jefferson's pairs. The waistcoat was also shortened about five inches, making the bottom edge terminate at the waist. The original waistcoat was significantly longer and had a center back vent.
These alternations changed how and when the waistcoat was worn. When the waistcoat was new it would have been part of a larger suit of clothing, possibly including a longer white woolen under waistcoat (also in Monticello's collection). These changes possibly altered the waistcoat so that later in life Jefferson could wear it underneath a shorter, newer-style waistcoat, which was perhaps not as warm as he wanted. Jefferson suffered greatly from the cold. He wrote on January 12, 1801, "I have no doubt but that cold is the source of more suffering to all animal nature than hunger, thirst, sickness, and all other pains of life and of death itself put together ."
- ↑ This article is based on Carrie Taylor, Monticello Research Report, 2002.