a grass lawn , the chlorophyll fades when grass is covered, all you need is a big enough neg
richard avedon did it when he was a kid ...
sun print on skin ... the negative to an arm lay out in the sun ...
people that restore stagecoaches would know where to get large sheets
of isinglass ( mica ) ..
some isinglass can be found here
years ago i found a dealer in the yellow pages and got some samples mailed to me.
website+blog: new entry galaxy direct postive paper
stuff for sale often times to benefit charity+relief efforts