10 apple seeds contain about 0.5mg of metabolized cyanide according to this article:
Cyanide lethality sits at a quantity of about 200mg for most adults according to this:
https://www.ncbi.nlm.nih.gov/books/NBK507796/
(200/0.5)*10=4000 apple seeds required for the average adult to reach a quantity that should be lethal—but that is assuming that the quantity of cyanide is perfect for every portion of 10 apple seeds and does not significantly vary depending on the kinds of apples sourced. Assuming any one apple you buy at the grocery store contains 10, you would need to extract the seeds from the cores of 400 apples. Also, apple seeds do not contain cyanide itself, but amygdalin which is turned into cyanide by chewing them.
You would have to grind, or manually chew, those 4000 seeds extracted from 400 apples. If you chewed them one after another, you would probably have to do it in a short timeframe, depending on the duration of cyanide in the system. How much of the amygdalin is converted into cyanide may also vary, and you would have to account for spillage from seeds you lose during the process from dropping them (practically impossible to perfectly account for 4000 seeds without equipment), from spit, or from inefficient intake for other reasons.
All-in-all it is theoretically low-key accessible since anyone can buy apples almost anywhere, but you would have to buy 400 of them or more and also process them without anyone else realizing. Since 4000 seeds almost certainly will not contain sufficient amygdalin, let's say you would need upwards of 4500 seeds just to account for various inefficiencies, and that's not to talk of the difficult intake process. I'm not sure whether you must specifically *chew* them to convert the amygdalin into cyanide, which if it were necessary would make this practically impossible to achieve in due time. If it isn't, I guess you could grind them into powder and turn it into a sort of drink? Just use another method to CBA.
