ANSWER: 
According to Anthony Montuori, Chief Inspector for the NY Board of Fire Underwriters, a 
lighting panel was restricted to 42 circuits as the result of a 1928 fire at the Waldorf Astoria. 
The cause of that fire was determined to be from an electric panel wired with type "R" cable 
whose overall heat load caused the fire.  The electrical apparatus of the time could safely 
handle a 42 circuit panel while a larger panel could not.