This paper explains how the eight lens elements of a 600 mm, f/2.0 ballistic camera are mounted and retained in almost perfect alignment. The total weight of the glass in this lens is 107 kg, the largest element weighing 21.1 kg. The lens is aligned to less than 3 µ of tangential distortion and the elements are supported in the mount in such a way that they are completely free of any strains. The near perfect alignment of the lens is maintained by soldering the lens elements into the supporting cells.
Leo G. Deterding, "High-Precision, Strain-Free Mounting of Large Lens Elements," Appl. Opt. 1, 403-403 (1962)