Mrs. Walker was my Sunday school teacher and we used to do this in the church kitchen, occasionally. This is my first memory of cooking that I cherish to this day. She keeps her age a closely guarded secret but is rumoured to be 115+ years old and perhaps, immortal. She has out lived three husbands and four children. She is still sharp as the Bowie knife she carries in her purse. I don't know why she carries a Bowie knife in her purse- but she always has. I asked her about it years ago and she said, "You would be surprised how often it comes in handy, Honey." I suppose it does, Mrs. Walker. God bless you. BTW- she is thrilled that I want to pass this on to another generation of schoolchildren. She was surprised that I remembered doing this with her over 35 years ago and was touched. When asked how to do it- she rattled off the instructions faster than I could write!
I've eaten this bag-n-boil recipe for 40+ years with no toxicity what-so-ever, obviously. If it was toxic... I would be in too poor of health to type.
Google the topic for yourself and make your own judgment. The danger is greatly exaggerated.