I had not only opportunity of seeing how different things have been made, but also manual work made me strong. - Jacob Leupold

Most often it is the case that people know that something big can be manipulated with it [i.e., the screw], but not how and in what way it is connected to time, and that untold time, and finally such force of machines, wheels, and shafts is necessary as cannot be produced nor be had.

[His work is addressed]... not to the learned and experienced mathematicians who are already, or should be, better acquainted with them... [and most of whom] have studied mechanics more as a subject of curiosity and a hobby, than with any view of service to the public. The people we had in mind were rather the mechanic, handicraftsman and the like, who, without education or knowledge of foreign languages have no access to many sources of information...