Rasaśāstra — Indian alchemy — processed mercury and metals into medicines now sometimes called ancient nanotechnology.
Rasaśāstra texts describe elaborate purification (śodhana) and incineration (māraṇa) of mercury and metals into 'bhasmas' (calcined ash medicines).
— Rasaśāstra (Āyurvedic alchemy) texts
Nanomedicine — metal/mineral particles at the nanoscale.
A popular claim that doesn't hold up — here's the honest story.
Rasaśāstra is a real and sophisticated tradition of chemical processing, and some modern analyses of bhasmas do find nanoscale particles — which has led to excited claims of 'ancient Indian nanotechnology.'
The honest, important caveats: the practitioners were following ritual-empirical recipes, not engineering nanoparticles knowingly; and crucially, mercury, lead and arsenic-based preparations carry genuine heavy-metal toxicity risks — multiple studies have found dangerous levels in some marketed products. So this is a card to read with care: a genuine, chemically intricate tradition, and a real research question about bhasma particles — but 'safe ancient nanomedicine' is an overclaim, and self-medication with metal preparations can be harmful.