How were mathematics recorded and communicated before the advent of Arabic numerals and algebra? How were equations organized and what symbols did they use to represent numbers, variables, and operations? Is there any symbol or convention that has remained consistent throughout mathematical history?

More can always be said, but you might find this thread from last week of some interest. The answers from /u/restricteddata and myself give some ideas about how some kinds of equations were expressed. You'll probably notice that one practice mentioned there is still in use today: the use of letters to mark points in geometrical diagrams. I can't think of any other notational practices that have persisted from antiquity to the present.