The salt trade is ancient. Since I’m thinking about gallivants a lot these days, I recall hearing about salt caravans out of the Sahara to ports in North Africa for trans-shipment to Europe. Even if I didn’t travel on a camel, seeing salt slabs in traditional boats on the Niger River . . . would suffice. Back in 1977 I was finished with a job in Cameroon and had the option of adventuring across the Sahara (hitchhiking) through another desert city called Agadez, and opted out. I still regret that choice sometimes. Two friends did it. I thought of this again recently while reading Vuvuzela Diaries.
What traveled north for centuries was salt as well as gold; what traveled south to Timbuktu were European “luxury” goods, including books. Here’s another BBC video on the scholarly libraries of Timbuktu.