The methods of magical performance are not usually seen as examples of folklore, but they have many of the same properties as a traditional story or ballad. Until recent times (and sometimes still today), techniques are passed along primarily orally, from one performer to another; many of the details of patter and other elements that make for an effective performance are also a result of each performer learning from what they have observed and selecting the elements which work the best for them. And so as with a lot of traditional material, effects pass through the years, sometimes lasting centuries but never quite passing on unchanged.
One of the oldest known magic effects is the cups and balls, which is still performed today. The plot is simple: the magician presents three cups and three small balls. The balls are made to vanish and reappear under the cups, building in complexity until the point where a sense of climax and resolution is achieved.
That's vague, I know. It's vague because the same effect has been done since ancient Rome (there's an argument that's only half the correct age, but the evidence is actually pretty terrible - a single image on a pyramid wall of somebody lifting something shaped like an inverted bowl), and the details seem to have changed continually ever since. The earliest detailed description we have comes from the early seventeenth century, and uses only the cups and the balls presented right at the start, even for its conclusion. By the nineteenth century, much larger balls start appearing from under the cups at the end; in the twentieth, the moves along the way start gaining in complexity, and the large balls are commonly followed with fruit. Other variations based on the classic have been invented as well, including a variant I'm fond of that uses only one paper cup, a signed and crumpled dollar bill as a ball, and a sharpie for a magic wand. Many of the specific maneuvers used in modern performances were not invented until recent years, and in a few cases they require specific features of the design of the cups or the balls which are not typical of seventeenth century equipment. Hocus Pocus Jr., author of a textbook of magic printed in 1605, includes in his treatise a number of other simpler tricks with balls, such as making a large ball pass through the table into a cup from below. He also offers various ways to make fake weapons with which the magician can appear to stab or cut himself and then be restored to full health. An even earlier book dealing in part with the magician's art, Reginald Scot's The Discovery of Witchcraft (1584), presents similar, along with card magic including a delightful four-ace trick and more.
There's another key way in which magic acts reflect the folklore of the day: the style of the presentation, which is only effective if tailored to audience expectations. The effects must defy any sense of the natural way of the world, In a more superstitious era when the supernatural was seen as the province either of educated eccentrics in the mold of Dee and Kelley or of dangerous goetics who made pacts with Satan, magicians learned to present themselves as somewhat ambiguous figures, clearly working with powers beyond normal human ken. Thus, Hocus Pocus Jr. encourages the performer to conjure forth a toad to claim as his familiar spirit, and to explain that the operation of the cups and balls is performed entirely by the balls themselves, which are sapient and follow the magician's instructions. (He even goes so far as to give the three balls individual names: Meredin, Benedick, and Presto John.) Magicians were also expected to be experts at gorily simulating various forms of injury to themselves, and then showing that by their arts they remained unharmed. It is in this era also that Scot offers us the first documentation of two-person telepathy effects in which the precise phrasing of questions clues in the person answering them. While Scot's version of this principle is used only to indicate whether a coin is heads or tails (by asking "what is it?" or "what ist?"), the principle has since been expanded - and it's likely it already was in Scot's own day; the writer was not a magician and in other places his informant on these matters, a French performer, seems to have withheld key details (for example, one of his card tricks requires a card to be forced but never indicates how this is to be done) in keeping with the usual magician's taboo against exposure. Coullew of Lorraine, a French performer active at about the same time as Scot was writing the Discovery, introduced an effect in which the magician uses his powers to safely catch a bullet fired at him, a plot which, performed in a different and safer manner, would become a signature of the Victorian performer Chung Ling Soo (arguably among the best magicians of all time) and which is performed using yet a third method by Penn and Teller in the present day. (Penn and Teller have, at least as of this writing, not yet experienced the same cause which led both Soo and Coullew to stop performing - both men died performing the bullet catch.) Again, the early performances relied on Coullew's claim to supernormal powers making it possible. Indeed, the title of Scot's book is based on the very same premise - by "discovery" he meant uncovering or exposure, and the purpose of the entire work was to show that those who seem to be witches are all frauds and it is unconscionable to continue executing them. It's not a claim anyone would bother advancing today, as magicians seldom claim to conjure forth the familiar spirits they received when making a pact with the Devil.
The modern cliche, then is a different image entirely - we tend to imagine the stage magician as an almost formal lecturer, dressed in evening wear. This image is derived entirely from the nineteenth-century performer Jean Eugene Robert-Houdin, who updated the image of magic and from whom Houdini derived his stage name. The look caught on, as did Robert-Houdin's style of presenting himself as a fit entertainer for all classes. In Robert-Houdin's day, this uniform made the magician's attire match that of his audience, and while it remains in the popular imagination, most of today's performers prefer something even more up-to-date. Magic has become casual, showing off the idea that the magician is an otherwise ordinary person with entirely extraordinary abilities. Robert-Houdin also pioneered the idea of selling magic very explicitly on its illusory nature, and today most magicians consider it unethical to genuinely pretend to any supernatural ability. Some, such as Derren Brown, go so far as to pretend they are performing feats of advanced psychology even when they are making use of impressive sleight-of-hand techniques. Others have started to rebel against the idea of reminding the audience that nothing out of the ordinary truly occurs, with many actively seeking out those effects with the strongest visual impact so that their spectators feel they have seen the laws of physics broken before their eyes.
It's this approach, which at once accepts the unreality of magic while at the same time embracing the magic itself as something that is very much part and parcel of the performer's (or at least their stage persona's) everyday life, that leads to performers replacing the purpose-built cups of a typical cups-and-balls routine with a to-go cup from Starbucks and the magic wand with a marker first pulled out to sign the borrowed dollar bill that serves as a ball. But it's the same modern desire for strong visual effects which leads that routine to end as it does: the bill is vanished, the cup is used to produce a perfectly intact lemon, and the lemon is cut open to reveal the dollar bill inside. The bill is, of course, uncrumpled, showing that it bears a signature proving it's the same one borrowed right at the very start. And while I personally love this particular updating of the oldest known effect in all of magic, it's far from alone: modern magicians penetrate signed cards into closed Ziploc bags, make decks cut themselves to set places, change their shirts in seconds without removing their jackets, and show a deck to contain one card turned face-down as a prediction of what the spectator would merely imagine. (I perform two of these myself now and then, and I'm working on learning that one with the lemon.)
The techniques used to achieve these wonders were not known to performers of the early modern period. Nor were they able to obtain the large mirrors or panes of glass that make many of the grand stage illusions of the nineteenth and early twentieth centuries work. But the impact of these effects is nothing more than a fulfillment of what magicians have dreamt of since the first human discovered the French Drop: a chance to show their audience a glimpse of something truly impossible.