[WP] A time traveler introduces medieval farming peasants to memory foam mattresses.

"Okay, but how do you make it?" The question rang out like a shot from the crowd.

The Salesman let the air settlr for a moment. His smile faltered a little. Finally, the questions and chatter moved on from who he was into sales.

Really, all the time travel baloney made his head hurt. He'd long since learned not to think about it. But, he was losing the thread and the silence had gone on too long. Closing a sale was always the same, no matter what era the rube lived in.

"Ah! That's the good part my friend. I make it so you don't have to. You can't make it. Your Lord can't make you make it. You just get the best night of sleep you've ever had with the patended lumbar support and memory beads." The Salesman turned and threw out his arm, taking in the dozens of sample mattresses he had laid out.

In another thankfully quiet moment one of the peasants who had volunteered to test the mattress began to let out a quiet snore. A sneer quickly turned up into a smile as the Salesman proclaimed, "See, you'll never rest better!"

It wasn't long before the Salesman had bartered and traded away all of the mattress. The small collection of coins and dry goods didn't matter much. What the Salesman was after was proof of product.

With a patent established in the 1700s it would be very easy to 'find' this ancient prior art and get the copyright claim overturned in court. His client would be happy. He'd get a little richer.

Sometimes the timelines wouldn't stick. Or it would be too hard for the Historians to find the art. Even when the Salesman gives the exact time and place.

Also, it still had to be believable to hold up in modern court. That's why the other ops the Salesman had been working on included moving rubber and petroleum products back a few centuries.

Those products were tricker because bigger players wanted that history fixed, but with enough massaging it was plausible that foam mattresses were around for a few hundred years. Everyone knew about the Antikythera mechanism, so why not a simple little mattress.

No one thought much about the Salesman after he left. No one could find him to buy more of the mattress. The mattresses wore out after a few years and quickly faded to memory, but they had existed. That's what the court records showed, at least.

Hydroponics is invented.