Best tip I can offer? Bruce Willis is about my size, with similar hands. So, figure the palm of his hand to be right about 4" across (one "hand" in traditional measurement, as it happens,) and extrapolate or compare with an image of him handling the stones.
The hardest part of figuring sizes is getting a reference to work from. It's helpful to know standard dimensions when looking at things:
- Standard doors are 6'8" (80") tall.
- The typical adult male hand runs right about 4" wide at the palm (not including the thumb)
- The typical indoor ceiling (not vaulted) is 7'11"-8'0" high.
- A typical interior door is 30-32" wide, typical entry doors are 36" wide.
One of my old party tricks was being able to look at a woman for about 15 seconds, and rattle off ALL of her measurements to within an inch or so, with her permission. Watching someone move about also lets me figure out whether or not they've had any "special" physical training (dance or martial arts,) and extended observation would allow me to discern more closely just what - and how much (although this is a rather different skill.)
I also find it handy to know my own body measurements:
- Palm of hand is 4-1/8" across.
- Full extended armspan, fingertip-to-fingerip, is 7'1"
- My shod foot runs 12" to 12-3/4" (depending on what I've got on my feet.)
- My thumbnail is 3/4" wide.
- Index fingernail is 1/2" wide.
With those as a baseline, I can figure out a great deal - just as I can with references in the scene. Knowing them on yourself allows you to figure proportions (roughly) on someone else, once you figure their basics (height and build.)
