I too have seen a warning with respect to the Mac Portable ADB, something in the Guide to the Macintosh Family Hardware about "could cause an unacceptable decrease in the +5 volt supply voltage and result in improper operation", but I have not seen a power spec.
I remember measuring and marking the draw on what I had years ago for mobile use with my Blackbirds but much of this has been given away. I do have:
an Apple Keyboard M0116 marked 55 mA
an Apple Extended Keyboard II M3501 marked 4.53 mA, (even without having any round symbol with the flat top on it, this looks pretty low power to me!)
an old wedge shaped A9M0331 mouse marked 73 mA,
two Apple wedge shaped G5431mice with round symbol marked 4.70 and 5.11mA.
I remember measuring and marking the draw on what I had years ago for mobile use with my Blackbirds but much of this has been given away. I do have:
an Apple Keyboard M0116 marked 55 mA
an Apple Extended Keyboard II M3501 marked 4.53 mA, (even without having any round symbol with the flat top on it, this looks pretty low power to me!)
an old wedge shaped A9M0331 mouse marked 73 mA,
two Apple wedge shaped G5431mice with round symbol marked 4.70 and 5.11mA.