During a conversation earlier today a couple of us were talking about operating old copying machines that used ammonia and were rather smelly and I doubt would get through modern health and safety rules.

I operated one during a holiday when I was in my late teens.  It was in the drawing office where my father worked and was used to copy architectural drawings that were done on large sheets of paper and I recalled that the largest sheets used were "double elephant".  While many people may remember the old British "Foolscap" paper size (about 8 inches by 13 inches, and which I think had a "fools cap" watermark), fewer people will remember the other sizes.  A quick bit of research on the internet produces the following - thanks to standardpostersizes.com

The smaller sizes of British Paper were

FORMAT	WIDTH X HEIGHT (MM)	WIDTH X HEIGHT (INCHES)
Foolscap	203 x 330 mm	7.992 x 12.992 inches
Quarto	203 x 254 mm	7.992 x 10.000 inches
Imperial	178 x 229 mm	7.008 x 9.016 inches
Kings	165 x 203 mm	6.496 x 7.992 inches
Dukes	140 x 178 mm	5.512 x 7.008 inches

Table of British paper Sizes

There were also sizes for bigger sheets of paper Imperial Sizes which also included a much larger size of foolscap.

FORMAT	WIDTH X HEIGHT (MM)	WIDTH X HEIGHT (INCHES)
Small Foolscap	337 x 419 mm	13.268 x 16.496 inches
Brief	343 x 406 mm	13.504 x 15.984 inches
Pott	318 x 381 mm	12.520 x 15.000 inches
Quarto	229 x 279 mm	9.016 x 10.984 inches
Monarch	184 x 267 mm	7.244 x 10.512 inches
Sheet, Half Post	495 x 597 mm	19.488 x 23.504 inches
Double Post	483 x 762 mm	19.016 x 30.000 inches
Super Royal	483 x 686 mm	19.016 x 27.008 inches
Broadsheet	457 x 610 mm	17.992 x 24.016 inches
Medium	470 x 584 mm	18.504 x 22.992 inches
Demy	445 x 572 mm	17.520 x 22.520 inches
Copy Draught	406 x 508 mm	15.984 x 20.000 inches
Large Post	394 x 508 mm	15.512 x 20.000 inches
Post	394 x 489 mm	15.512 x 19.252 inches
Crown	381 x 508 mm	15.000 x 20.000 inches
Pinched Post	375 x 470 mm	14.764 x 18.504 inches
Foolscap	343 x 432 mm	13.504 x 17.008 inches
Emperor	1219 x 1829 mm	47.992 x 72.008 inches
Quad Demy	889 x 1143 mm	35.000 x 45.000 inches
Antiquarian	787 x 1346 mm	30.984 x 52.992 inches
Grand Eagle	730 x 1067 mm	28.740 x 42.008 inches
Double Elephant	678 x 1016 mm	26.693 x 40.000 inches
Atlas	660 x 864 mm	25.984 x 34.016 inches
Columbier	597 x 876 mm	23.504 x 34.488 inches
Double Demy	572 x 902 mm	22.520 x 35.512 inches
Imperial	559 x 762 mm	22.008 x 30.000 inches
Double Large Post	533 x 838 mm	20.984 x 32.992 inches
Elephant	584 x 711 mm	22.992 x 27.992 inches
Princess	546 x 711 mm	21.496 x 27.992 inches
Cartridge	533 x 660 mm	20.984 x 25.984 inches
Royal	508 x 635 mm	20.000 x 25.000 inches

Table of Imperial Paper Sizes

Hope this is of interest.