The trick of the dissolved half-crown may be varied. In this case the coin should be marked by the owner. Upon finding it is not in the water when the handkerchief has been removed pretend to be anxious about its loss. Say you will pay it back in instalments, and offer a shilling towards it.
When the money-lender tries to take the proffered shilling it vanishes too. This is managed by boring a hole in the shilling, tying some elastic through the hole, and stitching the other end of the elastic up your sleeve. Then as soon as you leave hold of the coin it darts back up your sleeve.
“Has that gone too!” you exclaim.
“Well, we must try to find that half-crown; perhaps it is in this ball of worsted,” you say, as you pick one from the table.
Hand the ball of worsted to someone to examine and they declare that the coin is not in it. As you walk back to the table secretly exchange this ball for another.
Now this other ball of worsted has been prepared in this way. It has been wound round a tin tube about three inches long, a tube through which half-a-crown may be passed.
When you have the marked coin at the beginning of the trick you should have the ball of worsted in your pocket, and putting your hand there, should put the coin through the tube into the ball of worsted.
Then take the tube away and press the ball into its proper shape. It is this ball that you now place in an empty glass, and giving the end of the worsted to some lady in the audience, ask her to unwind it. As she does so the half-crown will begin to rattle upon the glass.

Excerpt from the book: Three Hundred Things A Bright Boy Can Do