Official system requirements were 32MB of real RAM with 40MB of VM. I actually ran it on my 1400 with that back in the day, and it was terrible. However a few months later I got my iMac, with 96MB of RAM, and it was much, much, much better. Even with 64MB, its really quite usable. Given that the average Mac back then had 32 - 64MB (or 128MB if you were lucky), they had to design it to be usable under such conditions.