and finally there is Tensfield by Martina Behm (of Hitchhiker Scarf and Hat fame)
The concept is easy, once you have the idea. It is that original idea that is so interesting. This hat can be knit in any weight yarn for any size head.
You start with knitting a triangle –

the triangle side
when it fits around your head you join the triangle in a circle

the side where the triangle is joined
after which you apply some basic arithmetic to calculate how many stitches are going to be in each section of knitting

looking where it starts to wrap
which leaves you at the end with a small area of three needle bind off and a top that looks a bit like the Hitchhat.

down from the top
As per usual, this is one of the many, many balls I have of Crazy Zauberball in an extremely ugly color combination knit on 2.5 mm needles. I forget how many stitches were on the needle at join point, but will try to remember to write that down the next time.
I have started in the upper right hand corner of page 1 (of 30) with a long, long way to go….

a few days into Chart 1