My cube uses Poser's internal scaling that is hardcoded into it.

Set Poser units to centimeter. Load a prop or a figure and move it 100 units up using the yTrans dial.

That distance is, according to Poser, 1 meter, because if you set the sytem units to centimeter, 100 units are 100 centimeters or 1 meter.

That's how I made my cubic meter cube, which then, because of the metric system that divides by 10, can be directly used to measure things by reading it's size percentages.

The advantage of a cube is that you can just as easily measure very big things like a car or a plane with it as very tiny things directly in all three dimensions.

Everything I use in my Poser world is scaled to real world sizes, from furniture to figures to props to vehicles. That way everything is in scale with everything else and nothing looks out of place.

As for circumferences or curves, that's a bit more complicated, but I could just as well construct some calibrated cylinders. I simply never had the need for it.

I think PhilC also has a tailor's tape prop that can directly measure irregular circumferences.