Alchemical Sun
Sol / Aurum
In his letter to Boyle of 28 February 1678/9, Newton describes aqua regis dissolving gold: alchemists' solar metal was not chemically untouchable.
Isaac Newton, letter to Robert Boyle, 28 February 1678/9, Cambridge University Library MS Add. 9597/2/18/62–65, paragraph 10 (Newton Project NATP00275).
A circle with a central dot, used for the Sun and gold in alchemical notation.
More context
The solar sign is a circle with a central dot. Indiana University's guide to Newton's manuscripts lists it as Sun / Gold. In the 1651 English Agrippa, gold belongs to the Sun because of its splendour. Solar things are associated with glory, victory and courage. The same metal also appears under Saturn for its weight and under Jupiter for its temperateness. These correspondences therefore overlap. Newton's letter to Boyle of 28 February 1678/9 describes aqua regis dissolving gold. The metal was a material substance handled with reagents, alongside its planetary associations.
Light
Agrippa associates solar things with glory, victory and courage.
Shadow
Newton describes aqua regis dissolving gold; the solar metal's splendour does not make it chemically untouchable.