I can visualise easily a $1000 or even a million dollars. A million dollars is actually quite small in $100 notes. But what about a trillion dollars? Not many people can.Even if you break it down the number is still pretty incomprehensible. It is a million million or a thousand billion. See still meaningless.
Thankfully someone has made a wonderful scale graphic of exactly what a trillion dollars looks like if made up of $100 notes. It is made up of double stacked pallets of $100 million each. The little red bit bottom left is a person.