The Houdini Drop Mount is a sidestyle mount. It is similar to the Double Or Nothing Mount.
Begin by throwing a breakaway. Wrap the string around your hands like you would for double or nothing, however, the first wrap should be around your freehand thumb, not your freehand index. So, the wraps should be as follows: freehand thumb (from underneath), throwhand index (from above), freehand index (from underneath). After the last wrap around your freehand index, mount the axle on the string farthest away from you, as in double or nothing.
To 'drop' this mount, release the string around your freehand thumb, you will end up in a trapeze mount. Good luck and have fun.