Re-viewing the episode (a friend has all the episodes of the original series), the Time Helmet has a small 'box' on each side from which extend backward three slender rods which seem to burn somewhat like sparklers (though they are larger than the fireworks I encountered as a child). It also had a barber pole that rotated, a dial to set the destination, two rods that extended upward (each having a short cross bar near the top) and were connected by a couple of wires, and a helical wire that formed a tall arch above the helmet (but below the two rods).
(http://www.twilightzonemuseum.com/show/images/3onceupon.jpg shows it [inactive] in the lower right corner of the picture.)
The episode is perhaps most distinctive in starring Buster Keaton and having the 1890s sections shown as silent film (with intertitles).
Yes, activating a Time Helmet indoors would be frowned upon.
I think I remember that episode! Didn't it have sparklers on top?
The pyrotechnics were very effective, but I think these days it would bring the wrath of the Fire Marshall down upon you if used in a public place.
Max, if you want sparks, nothing says sparks better than Jacob's ladder. That is, if you are comfortable having a few kV's that close to your brain. You could end up like the guy in One Flew Over the Cuckoo's Nest!
My ultimate geek hat would be this one:
(Or, you can just search for Johnny Mnemonic's helmet.)
I suppose it's useful to wear a hat that makes your competitors die laughing. I have two hats I use when faced with particularly difficult technical challenges. If the challenge involves detective work, I put on an authentic deerstalker, which makes its wearer feel like Sherlock Holmes. If the challenge involves exploration, it's time for the pith helmet.
Traditional, yes, but effective.