While going through the English in Use paper of a Cambridge advanced test, I came across these bits of information about ways of dealing with long exposure times in early photography:
"In the early days of photography, a stand or some other firm support for the camera was essential. This was because photographic materials were so insensitive to light that a typical exposure lasted several seconds. The camera would have to be held still for this time in order to obtain a sharp picture. The subjects also had to be still if their images were to register properly on the film. Some early street scenes included blurred, transparent, ghostlike images of people who wandered past while the scene was in the process of being photographed.
Studio portraits from the late 1800s show people posed rigidly, often leaning against furniture, which helped them to remain motionless. Since it was important to keep the head still, a support was often provided for the neck. Bright studio lights, sometimes produced by setting fire to a strip of magnesium or a small pile of magnesium powder, helped by reducing the required exposure time. These burned with an intensely blue flame that gave the necessary amount of light, though the smoke was unpleasant and there was also a risk of fire."