In 1801, James Monroe and Robert R. Livingston (the R. also stood for Robert, oddly enough) were sent to Paris not to buy the enormous swath of land subsequently called the Louisiana Purchase but to negotiate the purchase of New Orleans and the Mississippi Delta, thereby securing the lucrative Mississippi River shipping route. Negotiations fell through, and it wasn’t until Livingston returned in 1803 that Napoleon was so hard-up on cash due to the continent-wide war of conquest he was waging that he was willing to make a deal with the Americans. At the time, Livingston was authorized by Jefferson to spend up to $9 million in order to purchase New Orleans and the rights to the Mississippi. Since the US was planning on making a significant purchase from France, the delegation (Monroe rejoined Livingston in Paris shortly thereafter) travelled to Paris with $3 million in gold. In 1803,[gold was worth just under $20 an ounce](http://onlygold.com/Info/Historical-Gold-Prices.asp), which means they were travelling with almost 10,000 lbs of gold. This wasn’t even remotely close to the carrying capacity of freighters of the time. [“Tea Clipper” Frigates of that time could carry twenty times that weight.](http://www.tea.co.uk/tea-clippers).
Now, the negotiations took a turn when Napoleon decided he needed more money and offered the whole Louisiana Purchase for $15 million. Livingston and Monroe were authorized by Jefferson to spend up to 9 million on New Orleans and the rights to the Mississippi, so when given this offer, they had to make a decision without the President’s approval, and just couldn’t pass up the deal. Oddly enough, I just read the chapter describing the negotiations in Stephen Clarke’s very entertaining *1000 Years of Annoying the French*. According to Clarke, the purchase was paid for with the above-mentioned 3 million in gold as a down payment, with the cancelling of 3.75 million in debt that France owed to the US for French piracy on American ships since the revolution, and the rest was issued in bonds. Again from Clarke:
>French Banks were too nervous to accept the bonds, and two foreign banks had to step in to provide the cash. The first was Hope and Company, a bank based in Amsterdam but set up by Scotsmen. The second was a London bank, Barings. Napoleon was in such dire straits that he agreed to sell the bonds to the banks at a 12.5% discount.
I hope this answers your question sufficiently!