The drawing below is from Gustave Eiffel's book describing the tower that bears his name. There are 53 of them in total.
XXXI. Beams and Lattice Section. Data for the calculation of the framee
The board XXXI is one of the most important of the book, it is the one that gives the sections of the main elements of the structure of the Eiffel Tower. It shows the section of the rafters, which are the long metal bars starting from the ground and arriving at the top, and lattices, the beams forming caissons.
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