One of the untrue claims made repeatedly by Donald Trump as a candidate and then president is that Hillary Clinton “acid-washed” the hard drive containing her emails. She didn’t, and that doesn’t even make sense as a concept; Trump appears to have heard that Clinton used a software program called BleachBit to wipe the drive clean and that became “acid-washing” even though (1) there’s no actual bleach involved and (2) bleach isn’t an acid anyway. He also said that this process was very expensive, even though the software is free.

The point is that Trump will often seize upon an idea and it works its way into his political patter, accurate or not. Saying that Clinton acid-washed her server sounds better than saying she securely deleted her emails — or at least Trump seems to be convinced it does.

On Tuesday, another claim made its way into Trump’s rhetoric. See if you can spot it in this excerpt from Trump’s answer to a question at his bilateral news conference with French President Emmanuel Macron.

“When they made the Iran deal, what they should have done is included Syria. When I say ‘should have’ — before giving them, Iran, $150 billion and $1.8 billion in cash — $1.8 million in cash. You think about this. Before giving this kind of tremendous money, okay — $150 billion and $1.8 billion in cash — in barrels, I hear, it was taken out, and in boxes it was taken out — cash — they should have made a deal that covered Yemen, that covered Syria, that covered other parts of the Middle East where Iraq is — where Iran is involved.”

Trump has a habit of never admitting he made a mistake when he speaks. Introducing Macron, for example, he said that the French flag flying next to America’s was a symbol “of the world.” He then caught the mistake; he was supposed to say to the world. So he tacked it on — “of the world … and to the world” — despite the former not making sense. It’s possible, then, that Trump simply said “barrels” by mistake, which is why he then added “and in boxes.”

Or maybe he was trying to pretend that he hadn’t misspoken Tuesday morning, when he told the media that “we gave [Iran] $1.8 billion in cash. That’s actual cash. Barrels of cash. It’s insane. It’s ridiculous.” (The actual amount transferred appears to have been $1.7 billion.)

There’s no indication in news reports that any cash was actually transported to Iran in barrels. When a large payment was made to Iran in August 2016, it attracted a lot of media attention, in part because Trump continually railed against the payment. The size and manner of that payment is an admittedly complicated question, but there’s no evidence that I can see to suggest that any of it was transported in barrels. Trump’s insistence that he’d seen footage of the cash being flown to Iran led to one of his few admissions of error (though he didn’t exactly own up to the mistake).

So why is Trump now talking about barrels? It’s not clear. What is clear is that barrels would be a very weird way to transport it.

Consider the math. We’re know that there was transfer of $400 million in cash. It wasn’t sent in U.S. dollars but in euros, Swiss francs and other currencies. The largest denomination bill in which euros are issued is 500; the largest denomination in Swiss currency is the 1995 1,000-franc note. (We’re going to ignore the other currencies.) On average in August 2016, those bills were worth $560 and $1,030, respectively. Let’s further assume that there were an equal number of euros and francs. There’s no real merit to this assumption, but if you’re going to bother to waste space with euros that carry half the value of a franc, you might as well have a lot of them. You’d need 251,800 of each bill to add up to just over $400 million.

The question, then, is how many barrels you’d need for those bills.

A 500-euro bill has dimensions of 160 millimeters long by 82 millimeters wide by 0.11 millimeters thick. A 1,000-franc bill is 181 millimeters long by 74 millimeters wide by … well, it’s not clear. For the sake of argument, we’ll say the thickness is the same as the euro, but that decision can affect our calculations.

The total volume of these bills, then, is a bit over 734,000 cubic centimeters. This is … not very much space. It’s basically a cube that’s three feet on each side. If the francs are twice as thick as our estimate, that increases a bit. Now it’s a cube that’s about 3.4 feet on each side.

What kind of barrel Trump’s envisioning isn’t clear but, since this is Iran, let’s say it’s an oil barrel. Oil barrels hold 0.159 cubic meters. So our cash would fit in five oil barrels or, if you prefer, four 55-gallon drums. With space left over for packaging and, you know, air.

This is admittedly better than carrying it in those old-school silver briefcases. The site TV Tropes estimated that one briefcase could hold 6.3 million euros in 500-euro notes, so you’d need 20 such briefcases for your euros alone.

If the whole $1.7 billion was sent in cash (which isn’t clear), things scale up quickly. We’d need 1.07 million euro and franc notes, totaling 3.1 million cubic centimeters. That’s now 20 oil barrels or 15 55-gallon drums. Or 84 briefcases, just for your euros.

Instead of barrels, the money was apparently delivered on a pallet. (That’s how we sent cash to Iraq, too.) We don’t know the denominations of the bills used; clearly this would increase the amount of space they’d take up. But there’s also the issue of counting the money on the other end. A barrelful of money (a barrel of moneys) is either a waste of space, assuming rectangular packages of bills, or a big bird’s nest of paper. There’s a reason that banks don’t store their money in giant vaults like Scrooge McDuck: Good luck picking out the right amount from that mess.

We’ll see if the “barrels of cash” becomes part of Trump’s standard rhetoric around the Iran payment or, perhaps, if we’ll learn more about how that money got into those barrels. One thing that we can say with confidence, though. The money had not been acid-washed before it was sent.