Potassium nitrate...
...came in a little tin box like instant cappuccino, third shelf down just past the pepto bismal.
Amazingly enough, my sulfur was collected along the railroad tracks also.
Charcoal from the fireplace.
A wonderful book call "Fortunes in Formulas".
I lit what I thought (being a 9 yr old) was a small quantity in a glass jar. The resulting brilliant fireball caused the glass to shatter and fill my bedroom solidly with smoke.
Mom and Dad were sleeping in the next room. I quickly and quietly open all the doors and windows in the house and ran around fanning the vapors with a bath towel. Mom and dad never knew.
All subsequent experimentation was done outdoors.
(I hope Nick doesn’t read this thread… Sorry about the signal noise mate.)