sorry for terrible quality) The best trading route I've found so far. Buy empty mirror catch boxes at khans shadow, fill them by aestival, and sell them by the island of cats.
Steam Community :: Guide :: Save File Editing
Trade Route Strategies - Official Sunless Sea Wiki
Steam Community :: Guide :: Lore and Secrets of Sunless Sea
Trade Route Strategies - Official Sunless Sea Wiki
Trade Route Strategies - Official Sunless Sea Wiki
Trade Route Strategies - Official Sunless Sea Wiki
Sunless Sea (Ep. 4 - The Salt Lions Trade Route) - YouTube