A hydraulic lift is a simple machine that uses the transfer of pressure through an enclosed static liquid medium (usually an oil of some sort) to lift heavy machinery. In accordance with Pascal's principle, the pressure is transmitted from one end of the hydraulic lift to the other undiminished. When the area of the piston that receives the pressure is larger than that of the initial piston, the upward force exerted by the second piston is several times stronger than the downward force exerted on the first piston.
Cover one end of the plastic tube with the plastic bag. Seal the bag to the tube, making sure the seal is airtight.
Cut the top off the plastic bottle and make a hole in the base. Carefully feed the bag and the tube through the hole, so the bag sits in the bottom of the bottle.
Seal the funnel to the other end of the tube, making sure this seal is also airtight.
Put the spray can lid on top of the bag. Tape it down if desired.
Place the heavy book on top of the bottle (and therefore on top of the spray can lid and the bag). To demonstrate the lift, carefully hold the funnel upright and slowly pour water into it and through the tube.