Even transmutation, such as trying to turn lead into gold, is not inherently crazy. As we now know, all matter is made of the same quarks and electrons, and there is no law of nature to prevent convert one kind of atom to another. It is just extremely difficult, and only possible today in very tiny quantities in giant particle accelerators.
In a new collection of essays on The Unknown Newton, William R. Newman writes on Newton and alchemy:
For the tercentenary celebration of Newton’s birth, Keynes famously wrote in an address that:The other essays examine Newton's religious investigations.Newton was not the first of the age of reason. He was the last of the magicians, the last of the Babylonians and Sumerians, the last great mind which looked out on the visible and intellectual world with the same eyes as those who began to build our intellectual inheritance rather less than 10,000 years ago.The thrust of Keynes’s address was that the conventional view of Newton as a “rationalist, one who had taught us to think on the lines of cold and untinctured reason,” was not quite right and that the truth was more complicated: one of the greatest scientists of all time spent a large part of his most creative years on various unscientific quests, including a search for that most elusive of alchemical substances, the philosophers’ stone. ...
Newton’s alchemy fits neither the Keynesian picture of the English natural philosopher as “the last of the magicians” nor the Dobbsian view of his alchemy as a religious quest. Instead, Newton’s alchemical studies reveal an early modern scholar and experimenter hard at work in deciphering extraordinarily difficult texts and a natural philosopher attempting to integrate the fruits of this research into his overall reform of scientific knowledge. Although this view of Newton’s alchemical scholarship and experimentation may be less evocative than Keynes’s or Dobbs’s, it conforms more closely to the depiction of Newton familiar to scholars of his physics, mathematics, and biblical studies. Throughout his divergent activities, Newton remained wedded to techniques of analysis and understanding that would be familiar to most of us today. The apparent incongruity between Newton the scientist and Newton the alchemist dissolves when we acquire a deeper understanding of alchemy and of the man himself.