Sunlight and Stained Glass

Good Evening,

I'm an archaeologist using Radiance to do some daylight modeling in
medieval churches. I would like to include period-correct stained
glass in the windows (in this case 13th century grisaille). However,
I have no idea where to find information on the transmittance index
and other properties of stained glass.

Has anyone modelled something like this before?

Can anyone point me toward a resource that might have details on the
properties of stained and/or historic glass?

Thanks for your help.

-- Anthony