The spar-makers scribe scratches lines that follow the taper and designate where the addition four facets will be added. I have been using this same scribing tool for about 27 years ever since Tom Kiley showed me how to make one after learning from an article in WoodenBoat magazine. I started my professional furniture making career while working for Tom in Charlotte, Vermont in 1986.
Anyway, this tool was originally used to help make a tapering sailing ship spar even as it was cut with hand tools. In the case of the pencil post, we are leaving the facets on the post. If I wanted a rounded taper, I would just plane off all of the edges of the facets. The spar makers scribe is pictured below. The tiny points between the pegs are the scribes.
Back to beds. In the image below I am carving the fair curve of the lamb's tongue with a straight chisel. It takes a lot of practice to get this right but it is the best way to make this transitional part from facet to square.
The images below are of a completed lamb's tongue and facet. At the bottom is a video of finishing a facet with a hand plane.
Back to the shop to get this bed done.
Enjoy the darker evenings with the clocks changed back an hour. Personally, I'd rather that they did not change it so that I could get more done outside in the afternoons.