Puncturing a Sheep's Bladder
To set the mood, dress up in the clothing of a wizard and try to obtain a colorful, tall, conical hat. You will be using balloons for this trick, but if possible, research the appearance of a sheep's bladder, which would be the medieval equivalent to a balloon. Then either disguise the balloons or suggest to your audience that the balloons are actually sheep's bladders. Hand out the balloons to your audience, along with straight pins. Tell your audience members that before they push the pin into the balloon, they need to recite the proper incantation. They will then pierce the balloons, causing the balloons to pop. Finally you will recite your incantation and pierce your balloon, but the balloon will not pop because earlier you covered a small section of the balloon with transparent tape.
Turning Coffee into Coins
Both coffee and coins existed in medieval times, but to transform this modern trick into medieval magic you must use a wooden cup instead of the basic wax paper vending machine version. For safety reasons, ask an adult to help you cut the bottom of the cup. When the bottom has been cut, use a water-resistant glue to reseal the piece. Ideally you want the bottom to hold the liquid but also break when you add pressure. For the trick, pack the cup with a few inches of coins. Next pour coffee into the cup until the coins are hidden; don't use hot coffee. Also carve medieval magic symbols on the outside of your cup and wear a robe with long sleeves. Hold the cup for everyone to see, and then, reciting the magical words on the outside of your cup, push up from the bottom. By breaking the seal you will cause the coffee to drain (into your sleeve) and you will also push the coins to the surface.
Medieval Ash Trick
All of the supplies for this trick will have existed in medieval times, though you might want to substitute paper for parchment. First, verbally show your respect to the lords of dark magic. Next tell someone to think of a name and then write the name on a notepad. Tell them to rip the page from the notepad and have an adult burn the paper in an ash tray. Take the notepad from the person and begin to recite magical incantations while you unsuspectingly look at the top page of the notepad for the imprint of the name. You will also need to create another diversion while you write the name on your skin with either soap or wax. Finally, spread the ashes from the ashtray over your skin and the ashes will stick to the wax or soap, thereby highlighting the name. The most important part of this trick is creating misdirection.