Does anyone know a poem that has to do with sailing through a portal and discovering knowledge?

In the poem, the author says that once he sails through the portal, he will acquire all the knowledge he needs. But, after sailing through the portal, all he sees are more portals. And in fact, he has to choose a specific portal, so he ends up realizing that he will never know everything.

I thought it was Tennyson, but I can't find anything like that. I'm pretty sure the poet was British, though.