Dear Jonathan, 
The use of vi.sa for positive purposes is rare in Indian medicine (no trace as far as I know of the basic principle of homeopathy: similia similibus curantur).
Nevertheless, it is also an ingredient in one of the recipes of an Indrarasaayana according to Caraka. 
And a Rgvedic, longhaired muni apparently used  some kind of vi.sa to "fly"...  
As for the production of vi.sa, it will depend whether it is plant based or mineral based. 
For "faults" in mercury which give it a  vi.sa character according to Rasa;saastra see Oliver Hellwig's Wörterbuch der Mittelalterlichen indischen Alchemie and my review of it in IIJ a few years back. 
See also Meulenbeld's 5-volume History of Indian Medical Literature through the index of Sanskrit and Tibetan words in volume III.
Best, 
Jan



On Fri, 5 Jun 2020 at 19:42, Jonathan Silk via INDOLOGY <indology@list.indology.info> wrote:
Dear Friends
My friend Charles Ramble is working on a Tibetan text on poison. It mentions for instance 32 types. I am aware that (no doubt among others) Suśrutasaṁhitā in its Kalpasthāna has much to say about poison, but understandably, not how to make it. There seems to exist a term viṣaśāstra, but more I have not been able to discover. I feel I may have overlooked something rather well known.
I would be delighted both to learn more myself (no, I'm not looking to poison anyone!) and to pass along the information to Charles.

Very best,
Jonathan

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J. Silk
Leiden University
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Jan E.M. Houben

Directeur d'Études, Professor of South Asian History and Philology

Sources et histoire de la tradition sanskrite

École Pratique des Hautes Études (EPHE, Paris Sciences et Lettres)

Sciences historiques et philologiques 

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https://ephe-sorbonne.academia.edu/JanEMHouben