BTW, byZed and others, "stale" is an old word for urine (As in "the mare stood and staled.")
That's interesting, I can't find a reference as clear as stated above, but OED does give the origin of stale as "...describing beer in the sense of 'clear from long standing' ". So I read "stale urine" to mean "old, stinking rancid urine", when "settled urine" or "urine that has done set awhile" is probably more faithful to the old meaning you refer to.
...and as for the flat pan in the sun, my kids think I'm a little strange already, so if it doesn't work hidden under the porch, I'll have to settle for store-bought saltpeter.
