I remember when I was a kid, I had a book called "The Amateur Magician's Handbook", by Henry Hay, which described how lots of magic tricks and sleight of hand w

I remember when I was a kid, I had a book called "The Amateur Magician's Handbook", by Henry Hay, which described how lots of magic tricks and sleight of hand with cards, etc. were done, with detailed explanations and pictures. There was a section called "Heartbreakers", which contained tricks and techniques that were especially difficult to master. One of them involved predicting the outcome of a coin toss. The secret to it was that you just practice flipping and catching a coin to an extreme degree, aiming for consistency until you could replicate the action so precisely that the coin flipped the same number of times whenever you performed it. I practiced and practiced, but evidently not enough, because I could never do it. I found a bit of it online: "18. Heads-or-tails. This I take on the good and sufficient word of Eddie Joseph. He explains how it is possible to flip a borrowed coin, and call heads or tails correctly every time. "No trick to it -- just mechanical uniformity of action. It is obvious (when pointed out) that which face of the coin comes up depends simply on the number of revolutions the coin makes; and this depends on the weight of the coin, the height of the flip, and the force of the spin. "By always using one denomination of coin, you fix the weight. The uniform flip of your right thumb comes with practice. To get a uniform height, pick some marked point on the wall, and practice until you can toss the coin just that high every time. "You must also catch the coin on your left palm at exactly the same height each time -- your waist, naturally, is the easiest. "Once you attain true uniformity, you will discover that the coin always comes down showing the same face that went up, or else always the opposite face. Experiment with different heights of toss, keeping track of the way the coin comes down. Never vary the force of your thumb flip because that is the hardest to judge. "In performance, pick a mark such as a molding or picture frame on the wall of the room where you happen to be, make one trial toss to that height, and see whether the coin comes down the same as it went up, or opposite. Every time you toss to this mark afterward, the result should be identical.