Posing
Posing, adopting a pose.
The ESCI Russian artillery officer pictured here isn‘t actually looking through his military telescope, he‘s just posing with it. If the man really wanted to observe anything through the telescope, he would hold it with two steady hands in order to maintain the proper distance between the eye and the lens.
Source: Meyers Großes Konversations-Lexikon, 6. Auflage 1905–1909