The 91-year-old monarch noted the Imperial State Crown, which she wore during her coronation ceremony on June 2, 1953, is so heavy "your neck would break off".
In the documentary, the Queen also lifts the lid on the amusing trials and tribulations of being head of state - from the perils of wearing a heavy crown to her robes sticking to a thick carpet pile. The Queen, who stars in the programme due to air on Sunday, was aware of the general story, but did not know the details until told by royal commentator Alastair Bruce.
"Fortunately, my father and I have about the same sort of shaped head", the queen said.
"But once you put it on, it stays", she said of the famous crown.
"What fascinated me is the idea of the royal librarian gauging out the Stewart Sapphire, the Black Princess Ruby, the Edward-the-Confessor sapphire, just gauging them out with a pen nearly, and a knife, and sticking them into this little circular tin, and getting them ready so that they could be rushed away to an even more secure place".
"You have to take the speech up", she said, "because if you did [look down], your neck would break".
"There are some disadvantages to crowns, but otherwise they're quite important things".
The most precious jewels - the Black Prince's Ruby and St Edward's Sapphire - were even removed from the Imperial State Crown and kept separately in the biscuit tin "in case of emergency".
When referring to her coronation, the Queen told the BBC: "I suppose it marks the beginning of a life as a sovereign".
"It's fun to see I think", she said.
The Queen's crown jewels were hidden in a biscuit tin underground at Windsor Castle during World War II, according to a BBC documentary.
The Queen responded: "Yes, very unwieldy".
"I think what's so delightful is the queen had absolutely no idea this had happened", Bruce said.
The devout Christian faith of Queen Elizabeth II is a running theme on the new Netflix series "The Crown".
It is part of the Royal Collection season, in partnership between the BBC and Royal Collection Trust.
She adds when she sits in the carriage, she is very high, comparing her height to the coachmen several feet below.
The Coronation is screened on BBC One at 8pm on Sunday.