Castor beans contain ricin, which is a lethal poison. It just takes a single grain of sand to destroy someone. The toxin acts by inactivating ribosomes and stopping protein formation, which is a deadly issue. The poison has no solution, but it is possible to survive if the dosage is minimal enough. In 1978, Georgi Markov was assassinated with ricin. ¹⁾

Tetradotoxin or TTX is a potent neurotoxin that blocks sodium channels from shutting down the nerve passage between the brain and the body. A small dosage will induce weakness and lack of feeling, but just a little bit more paralyzes muscles that you use to survive. It takes about 5 hours for the full effect to take effect, but if the diaphragm ceases functioning, the lungs can no longer inhale or exhale, and you're dead. Alternatively, an erratic pulse may cause you to die faster. ²⁾

The poison is found on the skin of poison dart frogs. The frogs are not the toxin's origins themselves. It comes from the food they eat. The poison is a neurotoxin which affects the functioning of the sodium channel. The result is paralysis and a quick death. There is no antidote. ³⁾

Amatoxin is the deadly poison found in mushrooms. It could be enough to eat one mushroom to die. It's a common mistake to misidentify mushrooms. Amatoxin attacks the liver and kidneys. The damage ultimately results in a coma and death. This isn't a quick death. ⁴⁾

Cyanide is a toxin that bonds to iron in the blood, blocking oxygen from reaching the cells. In minutes, a deadly dosage kills. This toxin is therefore so widespread in nature that it is small quantities that the body detoxifies. It's present in seeds of apples, cherries, almonds, and apricots. ⁵⁾