I remember an alternate worlds book where the heroine is kidnapped as a bride for a "lord" who has to have a blonde wife to give him blond heirs. The kidnapper also ends up selling the lord a treadle sewing machine and brings needles by on a regular basis - at a HUGE price.
The lord's mother(?) finds that only the heroine can work the machine without breaking the needles (doesn't like it but those danged things are impossible to make or repair in a pre-Industrial Revolution world and seriously expensive). The machine is NOT used for utilitarian clothing but to make fancy things for the chapel and clothes for the lord and his family. Including the future babies that they are planning on the kidnapped "bride" to provide...
Unfortunately, I have no clear memory of how it ended - I might have read a sample and been unable to find the book or I read a novella excerpted from the book and didn't find it compelling enough to go looking for the full book. I do remember her thinking to herself that she was going to go insane spending all her time in a sewing room while the clothing for the estate was spun, woven, cut, sewn, and embroidered while the priest read the Bible (in Latin) to everyone. She spoke mostly English and some Spanish. The alternate universe spoke mostly Spanish (nobility), with Church Latin for some, and the local Indian tongues (Southwestern USA in our universe) and a lingua fraca mixing them - which she was having trouble learning without BOOKS to study.
Not time travel - but a fantasy - gems & gold were a way to transport wealth. But medicines and dye plants were a way to trade lightweight but valuable items without risking getting killed quite so often - as using the wrong ingredients would NOT get the desired results. Some dyes (Tyrian Purple) were worth their weight in silver or even gold as dried material even in our universe. Some especially favored colors might trade for more - and if you didn't know how to get the color right (water soluble? alcohol soluble? dry in sunlight? dry in the dark to avoid a color change? dye, dry, and then dip in another chemical to set the dye or change colors? You needed the trader or someone who knew what the dye was, the color it would produce, and how to get it to work properly or it was so much colored paste....or powder...or dried plant material with unknown properties.
Medicines even MORE SO.
Spices? That was what was driving the voyages of Columbus - a handful of peppercorns would buy a French serf's freedom at one point and spices were kept under lock & key - just like the silver plates & tableware, the vessels for the altar, or the lace & jewels of the rich.
Lace - thread might be relatively cheap - lace was fantastically expensive in terms of how long it took to make - and lace was another thing that would be relatively lightweight but valuable for the time traveler.