A kids book from 1972 proposed something similar, deliver packages by weighting them for neutral buoyancy and pumping them down pipelines[0]. [0]http://2010boo

A kids book from 1972 proposed something similar, deliver packages by weighting them for neutral buoyancy and pumping them down pipelines[0]. [0]http://2010book.tumblr.com/post/324091567/the-restaurant-kitchen-serves-thousands-of-people http://2010book.tumblr.com/post/324091567/the-restaurant-kit...