How effective were the poisons used by people like the Borgias?
Most of these poisons were derived from plants, and I doubt that much testing of them was done.
So, somebody like Lucretia Borgia-could she be pretty certain that the stuff she slipped into the wine, would kill the inteneded victim?
As far as I know - and I’m in no way an expert, but Wikipedia seems to back me up at least partially - the main problem with poison in that era wasn’t so much “is it effective” but “how do we tell if someone’s been poisoned”.
There were plenty of substances around at that time that could kill you quite certainly and unobtrusively if not quickly. The history of effective poisoning goes back at least to the roman empire.
Even earlier - it was known by the classical Greeks and one persistent ( if utterly inconclusive and unproveable ) hypothesis on the death of Alexander the Great was that he was poisoned, rather than died from a simple illness.
not quite the Renaissance but this must have worked pretty well in 17th century Aqua Tofana - Wikipedia . Unfortunately the article does not explain if it worked from a single dose like a good modern poison or if it required multiple doses. If the latter, it wouldn’t have been a problem for the wives who used it to poison husbands by administering it in their cooking.
Why do you doubt this? I’m pretty sure they’d test things on cats, dogs, peasants, that sort of thing. There were professional apothecaries who sold this sort of thing (ostensiably for rats etc) and were part of a quasi-guild structure, so knowledge was diseminated, I’m sure.
Plus, they weren’t all plants - the old favourite, arsenic, is a mineral, as were some others, and animal and fungal products were also used.
Besides arsenic, what substances would have been readily availabe to would-be assassins of the Renaissance era, which could be used to poison someone [relatively] quickly and [relatively] unobtrusively?
Aconite, yew, cyanide, poison mushrooms. That’s a good one, because you can mix them in with edible mushrooms.
Read this new book. It’s astonishing how many very poisonous plants are all around us.
Don’t forget about oleander.
When it doubt, refer back to the Classics : if hemlock was good enough for Socrates, it’s good enough for you 
Not cyanide as such i.e either Hydrogen Cyanide or the Na or K salts of Cyanide. HCN was only discovered in 1783. True, some cyanide compounds of plant origin might have been used, but I wouldn’t call them cyanide, exactly, nor can I find definite cites for cyanide poisoning that early.
Actually, arsenic was not a quick poison, thugh it was unobtrusive.
Hydrocyanic acid wasn’t isolated until 1783, but it was known that you could use peach pits or almonds to poison people in ancient Egypt, and people were grinding up peach pits for that purpose as far back as then.
I read that book last week! Very interesting.
There’s both acute and chronic arsenic poisoning, though. It can kill within 48 hours. Not as quick as cyanide, yes, but it doesn’t have to be the drawn-out death of e.g Napoleon.
I just added it to my wish list. Mr. Neville will really think I’m going to murder him when he sees that…
Death-cap and destroying angel mushrooms look like edible mushrooms (this is why they tell you not to gather mushrooms to eat unless you know what you’re doing). Death caps have been reported to taste pleasant. People pick and eat them accidentally to this day. You don’t need much- half a mushroom cap can be deadly.
Those mushrooms do take a few days to kill somebody.
They are native to Europe, so the Renaissance-era Europeans would at least potentially have had access to them.
The Roman emperor Claudius was supposedly poisoned with mushrooms by his wife.
Got to tell this old joke:
Two men talking, one mentioned he had three wives, all whom died.
Asked what happened, he said the first two died of eating poison mushrooms.
“That’s terrible,” his friend said. “What happened to the third wife?”
“She died of a fractured skull,” he told him.
The other guy asked, “How did that happen?”
“She would not eat the poison mushrooms.”
So I guess the stories are true. Lucretia Borgia had access to a lot of poisons, which if slipped into a glass of wine, would work quickly and efficiently!
Well, it’s true that Lucrezia Borgia could have gotten her hands on poison, but there’s no evidence that she ever poisoned anyone. Her first husband was convinced to give her an annulment. Her lover Perotto was stabbed to death, probably at either the Pope’s or Cesare’s orders. Her second husband was strangled by Cesare’s men while he was recovering from a beating they had given him, and her third husband survived her.