From “Learning how to Learn from Masters: Module 3.2. Motive and Representation”
This practice can be viewed as a continuation of the “envelope drawing” practice, and it begins in the same way.
Instead of stopping once the major parts and shapes of the figure are clarified, continue, focusing on further “internal” details and structures. The drawing will still look geometric, but it will be both more detailed (containing smaller shapes within the larger ones) and more concerned with the internal structure, not (only) the outer shape of the figure.
For these drawings, it’s better to use larger-format paper, so you have enough space for details.