A pineapple placed on the front gate of a returning whaling captain’s house symbolized a welcome to visitors who wished to view the treasures from his world voyages. Historical artifacts from these captains, who left the East End to hunt whales in hopes of becoming wealthy from their valuable oil, are on display in “Bridgehampton Whalers: A Farmer’s Life at Sea” at the Bridgehampton Museum, formerly known as the Bridgehampton Historical Society. Among them is a bottle of whale oil, a rare find according to Julie Greene, the curator, who offered a talk last Thursday on the exhibit.