Albert Magnus

Albert Magnus (Albert the Great) lived for 80 years in the 1200s, so maybe his age  is to blame for rumors of his quest for immortality. He was the greatest German philosopher and theologian of the Middle Ages and he also dabbled in alchemy, one of the fundamental fields of the time. 

There is not a lot of evidence that he was an alchemist, but many people have put his name on their alchemic books to add prestige, and have even credited  him with discovering arsenic and doing the first experiments with photosensitive chemicals. According to stories , Albert first witnessed the transmutation of gold from other materials. After this he  discovered the philosopher's stone and passed it on to his student Thomas Aquinas.