Since the idea of RPC goes back to 1976 and the first business use was by Xerox in 1981, I'm not exactly sure what qualifies as a really old tutorial.
Here are a few resources you might find helpful.
Power Programming with RPC (1992)
Remote Procedure Calls | Linux Journal (Oct 01, 1997)
Remote Procedure Calls (RPC) (1999)
Remote Procedure Call Programming Guide (PDF link)
rpc(3) - Linux man page
