The Theater of Hydraulic Machines, Volume II

...to know how not to concern himself with anything further than that he knows thoroughly what his machine should do theorice theoretically and what is lacking in praxi practice, and indeed that he knows which type of theory comes closest to it, or in what manner he can attain it, namely: through the avoidance or elimination of friction and the proper application of power; for these are the only means and ways. No one will ever achieve this completely, for it is an impossible thing, as little as two entirely equal weights on equal arms can move one another, even though this is the simplest machine with the least friction in the entire world. Or, an entirely new and hitherto unknown method must first be invented (which such artists boast of, but have never proven, even to the extent that the machine would simply run).

Here, I might easily fall under suspicion by many, as if I wanted to call into question or even deny what I have hitherto believed about perpetual motion. No, not at all, but one must make a distinction between a machine that is worked and arranged solely for the purpose of yielding such perpetual motion and also exerting some power, and ordinary machines, which consist of those regular simple or compound so-called five powers. For by these, most people also want to force more power than the power allows theoretice theoretically or according to the calculo mechanico mechanical calculation. For example, when one pretends to accomplish much more through an endless screw, flywheel, crank, and similar ordinary things than through a common winch and other simpler machines. But enough of this, because the inclined reader will find more in the appendix or in the discourse on the instruction of machine science, and perhaps in the next following part, where we shall write about lifting tools or better ways to bring forth or raise machines. (Such a part will likewise consist of some 50 copper plates and present all types of lifting tools, so-called cranes, winches, machines for erecting large obelisks, and so forth.)

As far as this Theatrum Hydraulicum is concerned, much that must remain left out here for lack of space will be in the Theatrum of...