You are attempting to murder or incapacitate enemy soldiers from the standpoint of a soldier or a low-level officer before they do the same to you. It will be challenging to find poisons with as rapid an effect. You will need either straightforward organic compounds or inorganic salts because it will be difficult to preserve them without causing the poison to break down. Both will be challenging to come by without having created chemistry.
Ancient Egyptians already understood how to extract cyanide from apricot kernels, so it’s not like they didn’t know how; they just needed a lot of apricots to make a potentially lethal arrow. An inorganic salt known as cyanide is stable, quick-acting, and lethal at sub-gram amounts. To construct a truly lethal arrow, I estimate you’d need to put 400 milligrammes to the arrowhead, which would mean processing 100 grammes of kernels for each arrow. This equates to 20 kg of apricots per archer or around half a kilo of apricots per arrow (40 arrows per archer was the norm). For a troop of fifty men, this equates to one complete wagonload (1 tonne) of apricots. Of course, there is effort involved in extracting the poison and coating modified arrowheads. The cyanide will probably need to be extracted, dissolved in water, mixed with arrowheads, and then the water will need to be evaporated away. This will take firewood and a suitable tub of some kind. All this effort goes towards making a troop of fifty soldiers more effective for five minutes of intense fighting and killing soldiers who would otherwise only sustain injuries. This is obviously too expensive and impractical for massed archers to employ extensively.
Far more difficult to obtain will be any other acceptable toxin. At least apricots were grown for human food; you didn’t need to hunt for a certain shrub to get maybe a fist full of belladonna berries, which is enough to poison a dozen arrows. The majority of poisons are like that; they are effective in killing people, but the logistics prevent their usage on a big scale.
Occasionally arrowheads were just dropped into rotting meat and over the course of a day or two became a bacteriological weapon. The catch here is that while an arrow wound was rarely fatal on its own, if it resulted in a terrible infection, you could bet on losing a limb (amputation), gangrene, sepsis, and death without medical care. Because it will take hours or days to work, this is more of a tactical weapon. It is helpful for raiders or in sieges, but less so in a crucial conflict.
Occasionally arrowheads were just dropped into rotting meat and over the course of a day or two became a bacteriological weapon. The catch here is that while an arrow wound was rarely fatal on its own, if it resulted in a terrible infection, you could bet on losing a limb (amputation), gangrene, sepsis, and death without medical care. Because it will take hours or days to work, this is more of a tactical weapon. It is helpful for raiders or in sieges, but less so in a crucial conflict.
