Apple Human Interface Guidelines (1987) [pdf]

If you like this, you might find the 1986 draft interesting:

https://www.brutaldeluxe.fr/documentation/cortland/v1_06_Hum...

I think the differences in the design principles are important. There is also a kind of informality in this document that I rather like. It isn't as dry as the final document became.

Website seems to be down, but Archive link works: https://web.archive.org/web/20211011041410/https://andymatus...