There is no mention of pressure in any turn-of-the-century maker's load recommendations, and I certainly agree that had shooters paid attention to those recommendations (and Western Cartridge had never introduced the Super-X loads) we wouldn't have images of cracked frames, or bent frame Tobins, or maybe even Long Cracked Smiths wink but I could be wrong.

This is Royal Gun Co.'s guarantee for the use of "proper and reasonable" loads

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Pressure data was not hard to find however. Sporting magazines eventually made it even to the wilds of western Minn. and Kansas, and were filled with warnings regarding the appropriate loading of the new fangled Smokeless Powders, which some ignored, with bad consequences, and the eventual warnings regarding pattern welded barrels

The Overland Monthly, Oct. 1895 “Smokeless Powder For Shotguns”
http://books.google.com/books?id=Wv0MAQAAIAAJ&pg=PA442&lpg
3 1/4 Dram Eq./40 grains DuPont Bulk Smokeless 1 1/8 oz. (1255 fps) = 7440 psi
3 1/4 Dram Eq./44 grains “E.C.” Bulk Smokeless 1 1/8 oz. = 7584 psi
Plus 10-14% for modern piezo transducer numbers
Too much stress cannot be laid upon the weakness that has been very prevalent to overload with nitro powders, and we admit that the temptation to the uninitiated and the misinformed to put in each shell, the same amount, measure for measure, as they have been accustomed to do with black powder is very strong. This is a great mistake and it would be well to bear in mind that in handling any of the nitro powders the shooter is dealing with an entirely different compound from the old article. To those who are as yet unfamiliar with the methods of handling and loading the nitro powders, if they will use common sense which is simply to read the directions that are plainly printed upon all packages of powder, and follow these directions as to the quantity without question, they will have no trouble with their ammunition...

Even the Sears catalog tried to warn folks

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But we gotta pay attention shocked
Hatcher's Notebook, 1966
https://books.google.com/books?id=yESNUKSg5aMC&pg=PA184&lpg
“E.C.” blank powder burns with extreme speed…to give a sharp report when it is not heavily confined. An enthusiast once got hold of some of this powder, being familiar with “E.C.” shotgun powder…and loaded a bunch of shells. To try out his new load he got out his fine Lefever gun, and put up a target in the shooting gallery to get the pattern. There was a terrific detonation, and a big piece was blown out the side of the barrel near the breech, flew across the room and buried itself in a wood bench.

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