This is the system that I have developed and use to invent figures without using models or reference.
The first page basically refers to the flaws in using the head as a unit of measurement.
The number one problem with systems based on the head is that the head is an ovoid and changes shape and dimension as it is rotated in space the second problem is that the landmarks fall on flesh i.e. nipples and navels which of course vary depending on sex, age, weight and position.
The system I have developed is based on a sphere which does not change shape or dimension when rotated in space and thus becomes much more useful to the artist as a system of creating the human form in space.
This page is one I did recently from memory.
This is a first page of a complete tutorial on the Cranial Index and the Cranial Grid.
As you can see the torso from the top of the head to the pubic bone is 5.5 units and the legs from the top of the great trocantor to the floor measures 6 units.
I am starting here with the spine and out from there.
This would be my starting point for a male figure <> I often make the lower leg of females about one half unit longer.