How much gold could fit in a portable hole?
The density of gold is 161.2 lb/ft^3. Pathfinder gp are 50 to the pound, so their volume is 0.000124 cubic feet each. The portable hole has a volume of (pi/4)*6^2*10 = 282.7 cubic feet. That fits 2,278,349 gp.
Using simple math, and packing the gold down to where there is no wasted space, the portable hole can hold 17,060,955 gold.
This fine black cloth, soft as silk, is folded up to the dimensions of a handkerchief. It unfolds into a circular sheet 6 feet in diameter. You can use an action to unfold a portable hole and place it on or against a solid surface, whereupon the portable hole creates an extradimensional hole 10 feet deep.
How much of it can you carry? A pouch, as described in chapter 5, “Equipment” in the Player's Handbook, can carry 1/5 of a cubic foot of volume or 6 lbs of gear. Of course, it's the latter figure that will be important, as 1/5 of a cubic foot of gold coins at normal packing density would weigh nearly 300 lbs.
When opened fully, a portable hole is 6 feet in diameter, but it can be folded up to be as small as a pocket handkerchief. When spread upon any surface, it causes an extradimensional space 10 feet deep to come into being.
There are no limits. The portable hole is simply massive. Once you have one, you're supposed to be well beyond the point where tracking storage space has any meaning, and the lack of specific rules is supposed to indicate that you just don't worry about it.
0000166 cubic feet... More like 8.1 million coins. Maybe as high as 9.3 million if the coins were packed fairly closely but not perfectly, maybe as low as 6.2 million if they were pretty loose. Or, as high as about 11.2 million if they somehow managed to get them stacked almost perfectly.
No, it can not. The portable hole(DMG, 185) states with my emphasis: You can use an action to unfold a portable hole and place it on or against a solid surface, whereupon the portable hole creates an extradimensional hole 10 feet deep. Only one person can open the portable hole, whoever has it must use their action.
The portable hole (DMG 264) (20,000 gp; 0 lbs.)
From as early as level 2, Artificers can create a Bag of Holding bomb at the end of each long rest. Placing a bag of holding inside an extradimensional space created by a Handy Haversack, Portable Hole, or similar item instantly destroys both items and opens a gate to the Astral Plane.
How much space do gold coins take up?
Gold - ~47,400 coins per cubic foot (neatly stacked) - ~36,180 coins per cubic foot (loose jumble) Platinum - ~52,630 coins per cubic foot (neatly stacked) - ~40,180 coins per cubic foot (loose jumble)
The one ounce coin, $50 face value, is 1.287 inches (32.70 mm) in diameter, contains one gold troy ounce and weighs 1.0909 troy ounces (33.931 g).
How much gold should you be giving your party? According to the Dungeons Master's Guide, the average amount of Gold you should budget for a campaign is between 29,933-66,410. If you don't have a copy of The Dungeon Master's Guide yet, you can pick one up at your local game store (support local!)
Placing a bag of holding inside an extradimensional space created by a Handy Haversack, Portable Hole, or similar item instantly destroys both items and opens a gate to the Astral Plane. The gate originates where the one item was placed inside the other.
An electrum piece is worth five silver pieces, and a platinum piece is worth ten gold pieces. A standard coin weighs about a third of an ounce, so fifty coins weigh a pound.
When deployed, it creates an extradimensional space six feet in diameter by ten feet deep. Folding the cloth causes the entrance to this space to disappear, but items placed inside the hole remain there. Sufficient air is contained in the hole to support life for up to ten minutes.
The Astral Plane looks like a great, silvery sea that goes on in all directions. Most of the Astral Sea is a vast, empty expanse. For the most part, the Astral Plane is devoid of gravity. There are dead Gods floating in the Astral realm with a few chunks of rock.
If you put two bags of holding inside a third, you're now carrying a bag with over twice the capacity. The fact a Bag of Holding never weighs more than 15 lbs means you could, hypothetically, put 33 bags of holding inside a 34th bag (this assumes the volume of a BoH is less than 2 cubic feet, which seems reasonable).
You can't use two infusion slots to have two bags of holding; once you make the first, that infusion is temporarily consumed and cannot be used on a second bag. You either need two artificers or a level 10 artificer with aforementioned Quiver of Arrow Stockpiling to do a free Baggie Bomb.
Starting at level 2 artificers can make black hole bombs for 4gp.
Does time pass in a bag of holding?
Time passes just the same for things inside the bag as outside. That means spells with durations last the same amount of time even if some part of that spell goes into a bag of holding.
Gold is so malleable that a single ounce of it (about the size of a quarter) can be beaten into a thin continuous sheet measuring roughly 100 square feet.
1 cubic foot holds almost 50,000 pennies, so that big pig would hold more than 200 million pennies!
Gold coins are made of gold. However, beyond this, we need to look at the actual purity of the metal. Gold is a relatively soft metal and can easily be scratched and lose precious micrograms of gold through wear and tear. Typically gold bullion is made of 24-carat gold, whilst coins are often made from 22ct gold.