I learned a similar but more cautious method in a jungle survival school: Step 1: Touch the plant with your hand, wait 1 hour for negative effects to develop.

I learned a similar but more cautious method in a jungle survival school: Step 1: Touch the plant with your hand, wait 1 hour for negative effects to develop. Step 2: If step 1 produces no negative effect, touch the plant to more sensitive skin, such as the inside of your forearm. Wait another hour for negative effects to develop. Step 3: If step 2 produces no negative effect, touch the plant to the area around your mouth. Wait another hour. Step 4: After touching your mouth with the unknown plant and seeing no ill effects, chew up a tiny bite of the plant in your mouth and spit it out, and then wait another hour. Step 5: Ingest a tiny amount of the plant and wait an hour for negative effect. Step 6: If no ill effects are felt at this point, the plant is likely safe for you to eat. This is a very long and difficult process, but it's the safest way to determine if the plant will kill you. If you see a lot of one type of plant that you think you might be able to eat, it's worth the wait to figure out if it's poisonous or not. Once you've identified an edible plant, you can continue eating it without going through this process again.