If you want to read a pretty good account of the atmosphere and attitude at the time, I highly recommend reading this book, if you can find a copy: http://talesofsfcacophony.com/

It goes into the origins of Burning Man, SantaCon, art cars – the whole deal. Burning Man in its current form started as “Zone Trip #4” or “A Bad Day in Black Rock”, organized by the Cacophony Society, after the burn at Baker beach was stopped by police.

If you want to read the original flyer for the event, the Internet Archive actually archived the whole of Rough Draft, which was the central organizing newsletter of the Cacophony Society. Here it is: https://archive.org/details/roughdraftoffici1171vari/page/n9...