[PW] Ink or pencil

[Fred Acerri]

Given today's modern inks, mechanical pencil leads, and pencils, and barring 
smudging or erasure, which media has the longer archival length.

This is for me so there is no big rush. It's just a question that's been 
bugging me and I have gotten a variety of answers but no fact source. I know 
when I go to an archival library I can only bring/use  a pencil in the 
reading room.

Thanks in advance
Fred Acerri