How did they measure sword blades?

[Helleri]

As far as I can see there are 3 reasonable ways to measure the length:
1) Along the spine side.
2) From the base to the tip.
3) Along the edge side (although this last one might require some care).

If we can assume that men of that time had the ability to reason as much as we do (which i think we can). What do you take as your solution when you have 3 results from approaching how you measure things with 3 methods? The reasonable thing to do (usually) is to take the median solution (or the solution that sits between two extremes but may not an exact median). Which begs the question. How long is it along the edge?

Also here is a method I use to measure blades that I included in a response video I made some time ago (I have it cued up to that part of the video): Blue Tape Method