How do I create a diagram in this specific style? I am unsure if this is the right place to ask this but I have seen this style of diagrams (shamelessly stolen from this question):



mostly in an academic setting, i.e. assignments, exams, publications, etc. Anyone have any idea how these diagrams are created. Are they created in Latex/Tikz/PGF, illustrator, paint, something else?
This definitely looks like LaTeX rendered fonts, however, there looks to be some imprecisions in the alignment of the wheels, which might imply they are organized by hand.

Perhaps it is a combination of LaTeX and Inkscape?  Inkscape can export to LaTeX-embeddable files so that LaTeX is in charge of rendering text.