When was the artificial horizon first required for IMC?

[flyer101flyer]

Does anyone have an easy way to peruse old FAA / CAA regs?

I'd like to know when, exactly, the artificial horizon or attitude indicator first became a required instrument for cloud flying in the United States. Surely well after WW2, no?

Did it become required for, say, airline transport or commercial flying in clouds before it was required for private flying in clouds?

Did it become required for cloud flying in gliders at the same time as it became required for cloud flying in airplanes?

(I know cloud flying in gliders is rare, but still the question must have an answer.)

But for starters I mainly just want to point down when this instrument was first required by the CAA or FAA for cloud flying in airplanes. If you have old copies of the FAR's / CAA reg that would shed light on this I'd love to hear.

Maybe we can pin it down by a process of elimination-- what is the earliest published material anyone has seen that lists this instrument as a required instrument for civilian blind flying in the US? What is this latest published material anyone has seen that does not list this instrument as a required instrument?

For that manner, when did the concept of flight by "Instrument Flight Rules" under formal control from the ground, versus VFR, first arise?

Thanks
Steve