I see doing a fast google search pound cake originally called for
A pound of flour
A pound of butter
A pound of eggs
A pound of sugar
One site says:
The name comes from the fact that the original pound cakes contained one pound each of butter, sugar, eggs, and flour. No leaveners were used other than the air whipped into the batter. In the days when many people couldn’t read, this simple convention made it simple to remember recipes.
Has anyone ever tried this? If so what does it taste like?
It tastes like pound cake, of course. 
In all seriousness, the 1 pound of each recipe works quite well and will provide you with a dense cake that has a delicate, not-too-sweet flavour.
Once you have the basics down, there’s lots of wiggle room for improvisation. A lot of people add 1 tsp of vanilla to the batter to give it a slightly nicer flavour, or citrus zest to make it tangy. Since basic pound cake can be a bit on the dry side, I usually also stir in 1/2 cup of sour cream for a moister result.
Just to clarify, you are using the pound of each ingredient, and then adding 1/2 cup of sour cream? Because that sounds like the awesome.
And, because I’ve never thought about weighing them, how many eggs make a pound?
I read a large egg weighs two ounces. Since there are 16 ounces in a pound that’d be eight large eggs.
But if you have made a cake with just one pound of butter, flour, sugar, and eggs, does it taste good, or do you need to put the vanilla for flavouring? Does it just taste like eggs?
I’ve done it both ways, with vanilla and sans. I prefer with. Also good with almond extract.
Here’s my family’s traditional Easter dessert, “Poached Eggs on Toast.”
You take you a slice of homemade pound cake, on a plate. You put half a canned peach in the center as the “yolk.” You surround the peach/yolk with whipped cream to make the “white.” You sprinkle you some nutmeg for “pepper.”
Don’t know where it came from, but it’s an old family tradition of ours.
More buttery than eggy. Of course, vanilla only makes it better.
Yup. Pound of each, plus 1/2 cup sour cream. It doesn’t really change the flavour - it just makes sure that the poundcake stays nice and moist.
The Joy of Cooking mentions the OP’s primordial recipe.