caput corvi

SEE:

CORVUS All refer to FEATHERS:
RAVEN i.e. SUBLIMATION
CAPUT CORVI

All of the CORVUS/RAVEN/CAPUT CORVI symbols are BLACK into WHITE:

See the HERMES BIRD in the Chymical Wedding of Christian Rosenkreutz (Foxworth translation, 1690) the Hermetic bird is described:

  "Now he was wholly black, and wild, wherefore other meat was brought him..., whereupon all his black feathers moulted again, and instead of them there grew out snow-white feathers. ... At the third feeding his feathers began to be so curiously coloured, that in all my life I never saw the like colours for beauty."  


Now make it thus. Take in the name of God the aforementioned Mercury or the naturall Water, the first matter of the Sages, Take of it as much as you will, and putt it into its vessell which must be pure, cleare, and cleane, and Seale it well above with the Sigills Hermetis, that the Mercury may not come out above, and sett it in its prepared place, that it may have a moderate heate every moment for a month. The naturall master saith That it may have its place warme whereby it works it self up and downe, so long til it ascend no more in the glasse, and begins to bee colle at the bottome, and becomes dry below in the glasse without the least moistnesse, like a black earth, that is caput Corvi, or an earthy dry element, for thus the true sublimation or exaltation of the philosophers is perfected as is said before. And in this sublimation is the true separation of the Elements, as the Masters say.

 A Chymicall treatise of Arnoldus de Nova Villa.

http://www.levity.com/alchemy/arnaldus_treatise.html