Transmutation of lead into gold isn't just theoretically possible - it has been achieved! There are reports that Glenn Seaborg, 1951 Nobel Laureate in Chemistry, succeeded in transmuting a minute quantity of lead (possibly en route from bismuth, in 1980) into gold. There is an earlier report (1972) in which Soviet physicists at a nuclear research facility near Lake Baikal in Siberia accidentally discovered a reaction for turning lead into gold when they found the lead shielding of an experimental reactor had changed to gold.