The drawing below is from Gustave Eiffel's book describing the tower that bears his name. There are 53 of them in total.
XX. Set of elevators Otis and Edoux. Vertical section along the diagonal of the stack l (North) to stack 3 (South)
This board is the first that shows the bowels of the tower. It describes the Otis and Edoux elevators, which were powered by a water system repelled by pumps. So there was a need for tanks, which are also described here. This plan is rather general, it shows more the implantation of these elements than it describes them, which will be done in the following boards.