The Isolator helmet, 1920s
The Isolator was designed to help focus the mind, particularly when reading and writing (literacy is hard work!). The helmet not only eliminated all outside noise, limited sight to just one line of text at a time, but it also pumped in oxygen. From the looks of it, the contraption would also assist in limiting hyperactivity by limiting movement, or, between weight and limited visibility, it would at least slow you down.
(I think I need one!)