In her last monograph in 1961, on the painter Nicholas Hilliard (c.1547-1619), the art historian Erna Auerbach makes that claim about one of his patrons, Henry Percy, 9th Earl of Northumberland :
"Henry [...] was called the "Wizard" earl because of his interest in science and alchemy."
All right, I've read something like it in Roy Strong's The Spirit of Britain: A Narrative History of the Arts (1999), to the effect that he had conflicting mechanistic and platonist worldviews, and that he shared Pico and Ficino's interest in the corpus hermeticum. Soit.
[By the way, is there and online version, or does someone have Sir R. Strong's own book on Nicholas Hilliard (1975) to shed some light on the problem ?]
But later Auerbach claims that Hilliard himself, not only had mere interest but practised alchemy :
"It is illuminating that [Thomas Vaughan, in his Anima Magica] should have referred to Hilliard, who, we know, had himself experimented in alchemy."
How so? The author's argument is based on these excerpts from legal documents quoted on page 32 & 33 :
Which made her conclude : "Here it becomes clear that Hilliard practised alchemy, an obvious sideline of the goldsmith's craft in the Elizabethan age".
But ... all the expressions she quote are stock phrases in the goldsmith trade.
Henry Percy, 9th Earl of Northumberland, built a substantial alchemical library. Much of this still exists in the family home at Alnwick Castle in Northumberland.
Percy was one of the members of the "Tower group" of alchemists along with Thomas Harriot and Walter Raleigh, when he was imprisoned by James the First. Life in the Tower of London seems to have been quite comfortable for the wealthy members of society unfortunate enough to have been imprisoned there.
Back in the early 1990s I visited the Alnwick collection of manuscripts on a number of occasions in order to create a descriptive catalogue and there are some great treasures there.