I'll bet you've been looking at old U.S. Civil War era photographs. So far as I know, it was just a convention of the period, much as men today will often pose with their hands in their pockets. (U.S. Grant often had one hand in his pocket and the other in his shirt. His wife Julia said that was just how he liked to look, even when President.) The main thing was to have the hands occupied with something. Notice how often Civil War soldiers posed with their weapons. Aside from wanting to look fierce and aggressive, it gave them something to do with their hands.
Hands are something of a nuisance, especially when you suddenly become conscious of them. Most of the time you're not thinking about them, but when you are, they become these huge hams on the ends of your arms. Good portrait photographers become expert, not just at posing the head and body, but at posing the hands as well. Nowadays we would resist having a subject pose with his hand in his shirt because it would make the photo look dated, but we might have a man thrust one hand in a pocket or hold his lapel in order to have his hands doing something. A favorite trick of mine with people who wore eyeglasses was to take them off and have the subject hold the glasses folded in one hand. This solved two issues: the hand was occupied, and I didn't have to deal with reflections and distortions of the face from the glasses.
he put his hand inside his shirt because he had a infection in his stomach and was scratching at the skin (because it was itchy)
pose
To sit for an artist is to pose.
the link below has info.
the kinda flat shoes with no heel.
Because of Napoleon. An artist who was painting Napoleon's picture, had trouble painting a realistic hand, so he told Napoleon to strike the pose, which you mentioned. The "hand inside shirt, over heart" pose.. I suppose many soldiers, wanting to be similar to Napoleon, copied his "pose."
Cow face pose
Pose with arrows in their hands? I'm not quite sure what you mean by this. They could be cosplaying as a character who uses arrows.
no he's like 12
The crab pose is when you flex your muscles with two arms in front the way Hulk Hogan used to do whenever he ripped off his shirt.
Pose with jazz hands! Or take a deep bow...
The picture you are referring to was taken when he was about to leave office. I do not know the reason for it, but it was not a habit. I would guess that is was the photographer's idea. Maybe he thought the pose looked statesmanlike a la Napoleon. In Napoleon's day or before, the hand in jacket pose was a classical pose, rather like having a hand on one's pocket for a relaxed look. The right hand is actually tucked into his vest, not his shirt.
Three sets of twins are to pose for photographs how many photographs are possible if each set of the twins are to stand close to each other
Brady shot standing pose photos that captured the solemn character of a revered military leader.
A headstand with weight balanced between the top of your head and hands is called a tripod headstand. This yoga pose requires strength in the arms and core, along with proper alignment for stability. It is important to practice this pose safely and with a spotter if needed.
Many white Army officers and southern politicians objected to the training of African American soldiers to use weapons. They feared that these black soldiers might pose a threat after the war.
Phalakasana is a yoga pose commonly known as Plank Pose. It involves holding the body in a straight line parallel to the ground, supported by the hands and toes. This pose helps strengthen the core, arms, and shoulders.