Rasahridayatantra 2.7.5

2.7.5

athavā dīpakayantre nipātitaḥ sakaladoṣanirmuktaḥ /
tiryakpātana tiryakpātanavidhinā nipātyaḥ sūtarājastu //

Or else, distilled in a lamp apparatus, freed from all defects, / the king of mercuries is to be distilled according to the procedure of transverse distillation.