Whilst researching The Lady's Slipper I had to look into the effects of orchid root when it was ground up and taken as medicine. This involved finding out what kind of solvents might have been used to keep the root in suspension, once it was pulverized, and then what sort of quantities might cause hallucinations or nausea if taken orally. Needless to say, I did not try it myself, but relied on various historical reports and on the medical journals of the time!
Weights and measures were different in the 17th century, for example barley could be sold in pecks or in pints, and with small quantities such as medicines the basis for an apothecary was the system of the "grain". Weights were as follows:
One scruple = 20 grains
One drachm = 60 grains
One ounce = 480 grains
One pound = 12 ounces = 5760 grains
The only liquid measure in the Apothecary System was the liquid grain which was the volume of water weighing one grain, but this was not introduced until much later in 1885. (The picture above shows a 17th century set of weights.)
As a novelist, although I might have wanted to use the term "scruple" for Geofrey Fisk to measure his medicine I chose not to, as "scruple" in modern usage has quite a different meaning.
Until the 20th century lady's slipper root - sometimes called moccasin flower - was used by Native Americans as a nervine and sedative, but modern pharmaceuticals with less side effects have replaced it today.
In Britain there have only been three deaths over the last fifty years that might have been caused by plants, but that does not mean you should not be wary of certain flowers and berries.
Hemlock is the most notorious killer, which causes paralysis of the lungs if ingested. In the Middle Ages a general anaesthetic was made out of hemlock, henbane and opium and used before surgery, particularly during amputations. Hardly surprisingly this kept the patient in a deep sleep for several days until the antidote was administered - vinegar!
Another poison, Deadly Nightshade or Belladonna, was used in the 17th century to increase a woman's attractiveness by dilating the pupils. It was dropped into the eyes, and caused blurred vision. If you were to drink it however you would suffer from convulsions, coma and finally death.
More information about poisonous plants from www.thepoisongarden.co.uk
fascinating talks about Garden lore