The Apple ][ has a monitor in ROM that allows to enter machine code directly. The legend says that for the Apple I, Woz knew the complete integer basic machine code and could type it live into the monitor.
Also, the monitor on pre-][+ machines with integer BASIC also had a mini-assembler, so short assembly programs could be typed in as such instead of keying in the bytes. Both versions of the monitor had a mini-disassembler.
On the other hand, I still remember at least a few 6502 hex opcodes, not that I have any use for that information anymore. The instruction set is small enough that it doesn't surprise me that Woz would have it memorized.
