About the rasa-viddha-tāmra-kanaka-nyāya,
for what it's worth, the irreversible transformation into gold of copper that is described as rasaviddha is indeed an image found in a number of old tantric sources, starting perhaps with the Sarvajñānottaratantra. Such gold, it is claimed, can never be transformed back into copper, just as recidivism from the state of Śiva-hood is impossible for the soul who has undergone initiation.
The maxim is typically formulated in this way (with some variants here and there, notably for the first word !):
rasaviddhaṃ yathā tāmraṃ hematvaṃ pratipadyate|
tathātmā jñānasambandhāt śivatvaṃ pratipadyate||
A number of passages are cited in footnote 904 of the translation of the Parākhyatantra (on verse 15.59).
In this stock formulation, by the way, nothing absolutely precludes the translation "penetrated"; but note that rasaviddha appears to be used in the Arthaśāstra (2.13.3) as the name for a type of gold (not as a qualification for copper), which is arguably evidence of a (rather old) semantic shift for the element -viddha in this context.
Dominic Goodall
On 13-Jul-2014, at 3:32 PM, Isabelle Ratie wrote:
1. As regards the first part of the analogy: Abhinavagupta also uses the image of mercury transforming copper into gold in Tantraaloka 5.151 (note the use of vedhita by the way): svaya.mbhaasaatmanaanena taadaatmyaṃ yaaty ananyadhii.h / "sivena hemataa.m yadvat taamra.m suutena vedhitam // (Cf. also TA 14.12). See also e.g. Yogaraaja ad Paramaarthasaara 96, p. 186: yathaa taamradravya.m siddharasapaataat suvar.niibhavati... I'm afraid these passages don't shed much light on the problems that you are trying to solve - still, maybe it is worth looking for other passages of this sort that could be more detailed?