The hand-in-waistcoat (also referred to as hand-inside-vest, hand-in-jacket, hand-held-in, or hidden hand) was a gesture commonly found in portraiture during the 18th and 19th centuries. The pose appeared by the 1750s to indicate leadership in a calm and firm manner. The pose is most often associated with Napoleon I of France due to its use in several portraits made by his artist, Jacques-Louis David, amongst them the 1812 painting Napoleon in His Study. The pose, thought of as being stately, was copied by other portrait painters across Europe and America. The majority of paintings and photographs show the right hand inserted into the waistcoat/jacket but some sitters appear with the left hand inserted. The pose was also frequently seen in mid-nineteenth century photography.
The pose traces back to classical times — Aeschines, founder of a rhetoric school, suggested that speaking with an arm outside one's toga was bad manners. Arline Meyer, in her essay "Re-Dressing Classical Statuary: The Eighteenth-Century 'Hand-in-Waistcoat' Portrait," notes the pose being used in eighteenth century British portraiture as a sign of the sitter's breeding. Francois Nivelon's A Book Of Genteel Behavior of 1738 noted the hand-inside-vest pose denoted "manly boldness tempered with modesty."
With the invention of photography, the pose continued but may have had an additional purpose in preventing blurring by maintaining the sitter's hand in a single place. The pose is commonly seen in photographs of members of the military, with a number of American Civil War photographs showing the pose (or indicated by three open buttons on a sitter's tunic).