Urine runs about 12-1-2, and wood ashes are about 0-1-3, so if you combine equal amounts of the two, you're still coming up short of 16-16-16. You can get even closer by adding some steamed bone meal, which is 1-13-0. If you make a 3:1:1 mix of ashes, urine and steamed bone meal, that adds up to 13-17-11, so you are close but not balanced. But it weighs a lot more than a sack of 16-16-16 fertilizer because of the "fillers" in the natural components (i.e., urine is 90+% water).
That's part of the lure of fertilizers produced by chemical processes, they can pack higher NPK numbers into a 40 lb bag. To be completely organic, using only bone and blood meals, ashes, and urine, to get an effective 16-16-16, you are going to be using several times the weight. Does that make sense for you?
