You're right. I know that CSS needs to be applied to a document; without a document there's nothing to be styled.

Still, to me saying that something is in "pure" CSS would imply that the HTML is not more complicated than e.g.:

  <div id=homer></div>

(I guess that making a drawing such as the ones in the OP using only one div would not be possible until browsers accept pseudo-elements to be defined on top of other pseudo-elements.)

I understand that by "pure" the author meant "without using images". But IMHO using dozens of empty div elements isn't "pure" CSS.

    > there is no HTML without CSS

    * HTML 2.0: 1995 
    * CSS 1: 1996

That must have been a hard year for HTML 2.0, not to mention half a decade for HTML altogether.