For grease lub of electric motors, virtually all the bearing manufacturers and motor manufacturers give instructions to pack the beairng housing some fraction full of grease (somewhere between 1/2 and 3/4 full.. toward the lower end for fast speed large bearings).

That seems to leave some room for interpretation. Let's say it's a horizontal machine. Would you:
A - Set the endbell on it's back and pack the cavity 1/2 deep. Then when endbell is assembled to bearing, grease is at the opposite end of the cavity from bearing.
B - Set the endbell on it's side and back the bottom half (3:00 to 6:00). Then upon assembly the grease will be in contact with lower half of the bearing.
C - Put small chunks of grease into the bearing trying to trap air between chunks so when the cavity is full you have only about 50% grease by volume and 50% air by volume, and grease will be adjacent to the beairng all the way around.
D - Something else?
(of course grease will be applied directly to bearing as well).

Are there any references that describe WHERE the grease should be packed in the bearing?

The rule is 1/2 to 3/4, but to 1/3rd!

How I learn to do it is as follows:

Pack the bearing full with grease; rotate the bearing two turns in one direction and two turns into the other direction; remove the excess of grease (don't push it back in); install seals; there you have enough grease in the bearing. An excess will cause heat.

Give me the bearing type and RPM, and I can give you an approximate amount for the first fill.

Thanks Ricky.

I think the method you describeddetermines how much grease ends up in the bearing itself. But I was interested in the "housing"... by which I meant the grease cavity in the motor endbell adjacent to the bearing.