I have the heaviest one of all: A 300mm/f:4.5 Xenar in a #5 shutter. Weighs a bit over one kilo, won't fit most lensboards... I use it on a Technika III 5x7 camera, which has big lensboards.

I also have a 360mm/f:5.5 Tele-Xenar in a Compound #3 which I use on my 4x5" Linhof Color. This uses standard Technika-type lensboards, so I can't see why you couldn't use one on most cameras? The lens is rather large and heavy, but it's a lot lighter than to carry the Tech5x7 and reduction back in case I need a longer lens...