Here’s a few random things that came to mind as I read this thread:
Marilyn Mach vos Savant has the highest recorded IQ at something around 220. At the age of 9, she got a perfect score on the Stanford-Binet IQ test three times in a row and demonstrated significant talent in many areas. The term “idiot savant” was coined for people that are similarly talented in only one small way. She’s one of the editors and columnists for Cosmopolitan magazine. Stephen Hawking is estimated to be somewhat higher, but no one knows how to test it.
IQ tends to increase with education and experience, and decrease with disuse. “Mental Muscle” is a pretty good analogy after all.
Einstein could keep complex problems in his head for ages, but did not know his own phone number. Asked for his number, he looked it up in a phone book. He then told the surprised recipient that phone books were readily available, so it made no sense to memorize the number when he might instead use that bit of memory for something more important.
Leonardo da Vinci is considered one of most intelligent people ever to live. This is based in part on his prolific works and the breadth of his application. He is also the only person known to have the ability to write separate documents at the same time, one with each hand, coherently and legibly.
In many cases, high intelligence is characterized by exceptional memory. The ability to retain details is critical for the efficient solving of problems. Brilliant inventor Nikola Tesla (father of AC current, fluid logic, radio, particle beams, microwave technology, energy-based weather modification, etc) was known to keep problems, notes, and processes in his head for years until he felt they were ready for construction and testing.
Many modern geniuses work for think tanks, the government, or large corporations. The products of their intelligence are usually incorporated into larger efforts, and are usually owned by their employers. This makes it quite unlikely that they will achieve significant notoriety outside the rarefied circles of their professions.