Transfer Measurement/Marking to a Live Edge

When working with a log with 2 or 3 square, flat sides and 1 or 2 live edges, what are some good ways to carry measurement markings from the flat sides onto the live edge?

I am interested in marking both parallel to and perpendicular to the grain direction. Straight lines are valuable, but answers should ideally have potential to give straight lines of known length. Some measuring tools I have access to: square, plumb line, chalk line, level, ruler, compass.

I am asking as a pure hand-tool user (that is, not about milling from a log). I am asking about laying out joints or other non-full-length geometries on stock with live edges. When I make a rip or a crosscut, I need to scribe a line on each face or else I won’t get it quite right.

e.g: I was cutting two rabbet joints for "waterfall" style legs on a thick slab table with two live edges. This required making a rip with both ends on live edge and the corners between rip and crosscut both fall on live edge. How would you lay out measurements when you need them on an irregular surface that can’t take a straightedge?