It's hard to see in this pic, but there's two rows of purl about 3/4 inch above the bottom ribbings. That's where I started to wander.
I used a sock weight hand-painted 100% merino yarn from Pollywogs. It took two skeins (each was 50 gm, 218 yds). I used the Singer 560, with the ribber. The ribs were done at tension 4/4 and the rest was done at tension 6.2.
Notice that I used sock yarn, and made socks. Must. Break. Out. of this. Rut.