the thickness of ones' pencil line was almost a mile
As a national service.e nav. I knew little and remember less. Now our nav tables were cork faced, this hopefully lessening the chances of pencil point breakage. We were taught to use 8H pencils as these drew a fine thin line and could be expected to remain sharp for a couple of hours or more. If turbulence started to cause you punching holes in your chart, you changed down to 6H or even 4H in extreme conditions. HB was only used to sign bar chits!
Now 1 fix every 30 minutes may sound like a leisurely life but far from it. So you have worked out where you were 6 minutes ago and now where you should be 6 minutes later. Unfortunately its time to start again because the whole process will take 24 minutes or if its bumpy and you have to take 2 minute shots of each star, there's only 3 minutes to spare!