Jack,
Whoever said he was a pro? In my post I specifically said "If he performed...." I certainly could be persuaded that Erdnase was merely a serious amateur rather than a professional performer that made his living from magic.
But, don't sell him short too quickly. Yes, the effects at the back of the book were virtually all lifted from other famous books of the era, but in almost every case Erdnase improved the effects significantly. In some, he created interesting presentations for tricks that before had none. For others, he improved the method. In a few cases, he even did both. At the very least this is someone who understood good, professional magic for the time. Whether he learned this from actual performing, from simply watching good performers, or whether he was just a naturally good judge of fine magic is impossible to know for sure.
As for the shifts being useful at the card table, I can only say that I emphatically disagree. First of all, the shift is used much less often than most magicians think. The reasons for this are several, but the main one is the relative rarity of the single-o cheater. Most cheaters work in teams of 2 or more, and no one shifts the deck (and risks a foul-up) when you can simply have a partner hit a brief, bridge or crimp for you.
Additionally, as written the SWE shift would flash the bottom card to every one sitting to the dealer's immediate left. This simply won't fly in a serious game, though I admit that in soft games the sky's the limit. In your description of the Longitudinal shift you would also flash the bottom card to the 1 seat. Don't be surprised if the guy in the 6 seat gets a little upset when he's not given the same advantage and mentions it to the whole table.
Finally, you're forgetting the cut card. In most of the serious games, a cut card is used to cut the card onto before dealing. In modern casinos this is usually a piece of red or green plastic, but a joker or advertising card can be used in private games. Think this is a relatively new development? It's mentioned in John Blackbridge's The Complete Poker Player which was first published in 1880. The section on cheating (and how to avoid it) can be found in chapter 3.
Just a quick note: It's my opinion that turn of the century poker players were much more sophisticated that we tend to give them credit for being. Although not exactly definitive proof, the following items constitute strong evidence in my opinion:
The Complete Poker Player also mentions disallowing the dealer to replace the cards "as they were," in other words, executing an apparently innocent looking "accidental" table hop. It also discusses having a confederate as a "takeoff man" to win the money.
In an 1864, UK edition of Hoyle's Modernized Games The notion of hitting a "breef" (English spelling) card is mentioned as well as corner crimps and bridging for hitting a cut. There is also a great mention of court cards being finally made symmetrical to prevent your opponents from being tipped off as you turned them around in your hand.
John Phillip Quinn's Fools of Fortune (1891) covers some of the same territory, but was written in Chicago (as opposed to the UK). He mentions shifting the cut, wide cards and bridging as ways of beating the cut, along with many other pretty sophisticated methods of cheating, to include a "roof." This was a partial cooler that was capped onto the regular deck during the cut. In a short-handed game I imagine this was pretty deceptive and devastating. Quinn also mentions the idea of shifting the cut after the deal to deliver 3 of a kind to the dealer's partner sitting to his left. (Hmmm, shifting the cards after the cut. Can you say "changing the moment?")
The 15th edition of The American Hoyle (1892) mentions disallowing a shuffle to take the place of a cut.
Koschitz's Manual of Useful Information (1894) mentions location work for the draw (holding good cards deep in the deck and keeping track of the number of cards used up so far to get to them -- probably done with a partner in the seat to your right and known as an "anchor play"). Other great items are the spread (and a way to prevent it on p. 40), the double-discard, cross-firing, running up and double-duking, and tell reading are all mentioned (though not described very well).
The Poker Manual (1901) disallows the dealer to simply pick up the bottom portion of the deck and deal from there; he must complete the cut before dealing. It also establishes that the cards should be cut towards the dealer by the person sitting to his right.
What do all of the above sources mean? Well, I think it makes a good case that those turn of the century players were smarter than we usually think, and that you weren't likely to fool the more experienced card players of the day (even the non-cheats) with raw technique, unless you were very, very good. There's no doubt that Erdnase was probably good enough in many cases, but I think the structural problems of almost any shift (to say nothing of the ones he put in the Legerdemain section) makes it a tough move to use at the card tables of the late 1800s and early 1900s.
He even said so himself on p. 95: "There are many methods of performing the manoeuver that reverses the action of the cut, but in this part of our work we will describe but three which we consider at all practicable at the card table. This artifice is erroneously supposed to be indispensable to the professional player, but the truth is it is little used, and adopted only as a last resort."
Does it get any clearer than that?
Jason
PS: A quick note, with the exception of the UK edition of Hoyle, I tried to use sources that were published in the time that I thought Erdnase might actually have been playing, or just a few years prior. But almost all of the moves listed above are actually in print much earlier, which just goes to show that most of the good cheating moves were well-known to serious card players. Stocks, double-duking, strippers, briefs, seconds and bottoms, crimping, cold decks, holding out, false shuffles and cuts, shifting the cut (he mentions that there are a "dozen different ways"), marked cards, the double discard, shifting the cut after dealing, the Bug, and the aforementioned idea of an "anchor play" for locating good cards on the draw are all mentioned in How Gamblers Win: or the Secrets of Advantage Playing which was first published in 1865.