To quote my own choice. Did you know that astronomers at Palomar while observing had to wear a helmet & sit in a chair strapped with a seat belt. Astronomers would fall out of seat thus get injured. Using a Discovery 12.5" f/5 Dob here at home was a "Wow" factor. What do you call a 200" scope???
I was a graduate student in astronomy at Caltech 1982-88 and from first-hand experience[*], I can confirm that the observer's chair in the prime focus cage did at one time have a seat belt. But I've never heard of a helmet requirement. However there was / is a requirement to empty one's shirt and jacket pockets prior to climbing inside, so there's no risk of anything falling out while up above the primary mirror ... (the primary's protective mirror cover is closed during all trips by personnel into / out-of the prime focus cage, of course, but it's a prudent rule nevertheless).
The bottom of the chair is attached to a semi-circular tube (supported at each end by bearings in a yoke-mount arrangement) so it can be raised or lowered in elevation by a hand crank. The two diametrically-opposite yoke supports are in turn attached to a circular racetrack around the inside circumference of the cylindrical cage, such that the chair can be rotated 360-degrees around the optical axis and be locked at any azimuth by the observer --- when the telescope is being used at a large zenith angle, it's most comfortable for the observer to be oriented with gravity at their back in the seat (as in a recliner chair), rather than having to support one's body weight over the guide eyepiece with gravity pulling one forward ....
This Russel W. Porter hand-drawn illustration gives a sense of the space, and the yoke-mounted semi-circular tube I mentioned can be seen below the man's left elbow. It appears he is guiding by translating the photographic plate-holder assembly in X and Y (at the prime focus -- notice the white lines and arrows marking the beam path to the prime-focus field of view) to keep the guide-star centered, but with more modern instruments located at prime focus, obviously guiding (in the rare cases it needs to be done visually) is performed with a push-button hand-paddle to move the telescope in R.A. and Declination. (Behind the plate holder assembly against the inside wall is one of the yoke bearings I mentioned earlier). Over the end of the prime focus cage in this illustration is the original hand-rail / guard-rail to assist one in getting in or out of the cage, and into a dogleg-shaped-catwalk elevator that moves along a track attached to the inside of the dome near the dome shutters. By my time there, this hand-rail / guard-rail had been redesigned to better facilitate overhead crane lifts of heavier equipment in and out of the cage for mounting onto the prime focus pedestal. Here is what the redesigned version looked like, with its larger horseshoe-shaped opening in the center, directly above the prime focus pedestal):
(Incidentally, the individual in the grey suit-jacket visiting the prime focus cage in the photograph above, Caltech Emeritus Professor of Astronomy Jessie Greenstein, was 85 years old at the time (1995); see: https://www.tommcmah...-telescope.html )
The most recent pictures I've seen of the Palomar 200-inch Hale Telescope's prime focus cage show no hand-rail / guard-rail over the end whatsoever, which I interpret to mean that there is not longer any need for anyone to be in the prime focus cage at night with their eye at a guide-eyepiece --- today's prime focus instruments have all had video guide-camera capability and/or auto-guide capability for many years now. Riding the catwalk-elevator to the prime focus cage at the top of the 200-inch telescope is necessary only for equipment installation, care, and feeding, so the topmost hand-rail / guard-rail has been removed and replaced by two steel cables:
(The photo above, taken in the summer of 2003, shows Valdosta State University (Georgia, USA) senior undergraduate astronomy-major Melissa Williams sitting in the prime focus cage next to the Large Format Camera, which consists of six 2048 x 4096 -pixel CCDs, covering a roughly circular area, 25 arcminutes in diameter at a scale of 0.18 arcseconds per pixel. The camera is liquid nitrogen cooled. Source: http://www.astrometr...ges/200310.html )
Thanks for indulging my reminiscences here -- the 200-inch definitely is a one-of-a-kind classic marvel of 1930's engineering.
[*] In the early 1980s, my graduate faculty advisor at Caltech had an observing run on the 200-inch to observe galaxies using the first CCD-based faint-object spectrograph available at Palomar, dubbed the PFUEI (for "Prime Focus Universal Extragalactic Instrument" -- briefly described starting on page 5 of the PDF conference paper found here: https://authors.libr...ech.edu/101955/ -- the acronym PFUEI was literally pronounced "phooey" : - ), which did not have a video guide camera for remote guiding from the control room nor any auto-guide capability, and therefore my advisor needed an assistant to perform this function manually at the off-axis eyepiece in the prime focus cage, along with a few instrument-configuration changes over the course of each night. (Obviously I was a more-than-willing eager volunteer for this 3- or 4-night assignment. The target galaxies being faint, the nights requested were "dark time" -- i.e., new moon or crescent moon phases. A once-in-a-lifetime experience, to be sure ... even if all I got to see through the guide eyepiece were random stars near the target galaxies ....).