In Ayurvedic medicine, the traditional medical lore of Hinduism, rasa shastra is a process by which various metals and other substances, including mercury, are purified and combined with herbs in an attempt to treat illnesses. Its methods correspond to the alchemy familiar in the Mediterranean and Western European worlds.
History of development of Rasa Śāstra
The credit of developing Rasa Shastara as a stream of classical Ayurveda, especially in fulfilling its healthcare-related goals, goes to Nāgārjuna (5the Century CE). 
Important Classical Textbooks on Rasa Śāstra
Rasa Hridaya Tantra
It was created by Shrimad Govind Bhagvatapad- guru of Shankaracharya in around 7th century.It contains elaborate description of dhatuvada ( metallurgical processes to transform mercury into higher metals as gold or silver). It is well organised and complete. A Sanskrit commentary on this text was contributed by Shri Chaturbhuj Mishra under the name of Mugdhavabodhini.
Rasa Prakasha Sudhakara
It was created by Aacharya Somadeva in around 12th or 13th century. It contains 13 chapters which give elaborate description of mercury and its processing for medicinal use; definition and description of equipments and Puta ( temperature requirements and regulation during processing ).It can be inferred that at the time of its creation the Gurukula system of education was prevalent as it contains description about Shishyopnayana samskara ( ritual performed at the time of admission ). Specific contribution of this text include high degree of organization followed during compilation and description of 64 divya-aushadis (drugs with miraculous effect) for the very first time.
Rasa Ratna Samuccaya
The methods of rasa shastra are contained in a number of Ayurvedic texts, including the Charaka Samhita and Susruta Samhita. An important feature is the use of metals, including several that are considered to be toxic in evidence-based medicine. In addition to mercury, gold, silver, iron, copper, tin, lead, zinc and bell metal are used. In addition to these metals, salts and other substances such as coral, seashells, and feathers are also used.
The usual means used to administer these substances is by preparations called bhasma, Sanskrit for "ash". Calcination, which is described in the literature of the art as shodhana, "purification", is the process used to prepare these bhasma for administration. Sublimation and the preparation of a mercury sulfide are also in use in the preparation of its materia medica. A variety of methods are used to achieve this. One involves the heating of thin sheets of metal and then immersing them in oil (taila), extract (takra), cow urine (gomutra) and other substances. Others are calcined in crucibles heated with fires of cow dung (puttam). Ayurvedic practitioners believe that this process of purification removes undesirable qualities and enhances their therapeutic power.
Modern medicine finds that mercury is inherently toxic, and that its toxicity is not due to the presence of impurities. While mercury does have anti-microbial properties, and used to be widely used in Western medicine, its toxicity does not warrant the risk of using it as a health product in most circumstances. The Centers for Disease Control and Prevention have also reported a number of cases of lead poisoning associated with Ayurvedic medicine. Other incidents of heavy metal poisoning have been attributed to the use of rasa shastra compounds in the United States, and arsenic has also been found in some of the preparations, which have been marketed in the United States under trade names such as "AyurRelief", "GlucoRite", "Acnenil", "Energize", "Cold Aid", and "Lean Plus".
Ayurvedic practitioners claim that these reports of toxicity are due to failure to follow traditional practices in the mass production of these preparations for sale, but modern science finds that not only mercury, but also lead is inherently toxic. The government of India has ordered that Ayurvedic products must specify their metallic content directly on the labels of the product; however, M. S. Valiathan noted that "the absence of post-market surveillance and the paucity of test laboratory facilities [in India] make the quality control of Ayurvedic medicines exceedingly difficult at this time.
- "Rasa Shastra – Freedom Vidya". Shrifreedom.org. Archived from the original on 14 November 2012. Retrieved 2015-02-25.[unreliable source]
- "Scientific Basis for Ayurvedic Therapies - Google Books". Books.google.com. 2003-09-29. Retrieved 2015-02-25.
- Savrikar, SS; Ravishankar, B (2011). "Introduction to 'Rasashaastra' the Iatrochemistry of Ayurveda.". African journal of traditional, complementary, and alternative medicines : AJTCAM. 8 (5 Suppl): 66–82. PMID 22754059.
- Mishra, p. 86
- Mishra, pp. 86-88
- Mishra, pp. 87-88
- Mishra, pp. 88
-  Archived 7 May 2009 at the Wayback Machine.
- [dead link]
- "Lead Poisoning Associated with Ayurvedic Medications - Five States, 2000-2003". Cdc.gov. Retrieved 2015-02-25.
- Catherine A. Hammett-Stabler, Herbal Supplements: Efficacy, Toxicity, Interactions with Western Drugs, and Effects on Clinical Laboratory Tests (John Wiley and Sons, 2011; ISBN 0-470-43350-7), pp 202-205
- Hammet-Stabler, pp. 205-206
- Valiathan, M. S. (2006). "Ayurveda: Putting the House in Order". Current Science. Indian Academy of Sciences. 90 (1): 5–6.