Question: What did IWF rules say about an athlete's knees and elbows?
About the article "Olympic weightlifting", section "History".

Candidate passages:
Competition among people concerning who can lift the heaviest weight has been recorded in diverse and ancient civilizations as early as the earliest known recordings of such human events, including those found in Egypt, China and in ancient Greece.
Today, the modern sport of weightlifting traces its origins to the European competitions of the 19th century.
The first male world champion was crowned in 1891.
Women's competition did not exist, and the weightlifters were not categorised by height or weight.
The first Olympic Games of 1896 included weightlifting in the Field event of the predecessor to today's Track and Field or Athletics event.
During the 1900 Olympic Games, there was no weightlifting event.
Weightlifting resumed as an event, again in Athletics, in 1904 but was omitted from the Games of 1908 and 1912.
These were the last Games until after the First World War.
In these early Games, a distinction was drawn between lifting with 'one hand' only and lifting with 'two hands'.
The winner of the 'one hand' competition in 1896 was Launceston Elliot, while the winner of the 'two hands' event was Viggo Jensen of Denmark.
In 1920, weightlifting returned to the Olympics and, for the first time, as an event in its own right.
At these Games, which took place in Antwerp, Belgium, fourteen nations competed.
The competition lifts were the 'one hand' snatch, the 'one hand' clean and jerk and the 'two hands' clean and jerk.
At the next Olympic Games, in Paris, France, in 1924, the 'two hands' press and the 'two hands' snatch were added to the programme, making a total of five lifts.
In the Olympic Games after 1920, instead of requiring all competitors to compete against each other regardless of size, weight classes were introduced and, by the 1932 Olympic Games, weightlifting was divided into five weight divisions.
In 1928, the sport dropped the 'one hand' exercises altogether leaving only the three remaining exercises: the clean and press, the snatch and the clean and jerk.
By 1972, the clean and press was discontinued because athletes started to push with legs and bend backwards instead of strictly pressing the weight overhead, and this left the sole elements of what is today's modern Olympic weightlifting programme – the snatch and the clean and jerk.
The snatch entails pulling with a very wide grip the barbell overhead without pressing out with the arms.
It is a very precise lift that can be nullified by a lack of balance of the athlete.
The clean and jerk is more forgiving using a narrower grip pull the bar to the shoulders and then using the strength of the legs push until arms reach full extension without a press out.
A competition for women was introduced at the 2000 Olympic Games in Sydney, Australia.
As early as 1987, there were official world championships awarded to women weightlifters such as Karyn Marshall and Judy Glenney.
In 2011 the International Weightlifting Federation ruled that athletes could wear a full-body "unitard" under the customary weightlifting uniform.
Kulsoom Abdullah became the first woman to do so at the U.S. National Championships that year, and athletes are allowed to do so at the Olympics.
IWF rules previously stated that an athlete's knees and elbows must be visible so officials can determine if a lift is correctly executed.
WVR's rules differ somewhat from the unified rules of mixed martial arts.
Among the differences are the allowance of knees and stomps to the head of downed opponent while elbows to the head and soccer kicks are prohibited.
Similar to the Unified Rules, fights have 3 rounds each lasting 5 minutes. 
Slamm MMA fights were conducted under different rules from the North American Unified Rules.
Among the differences were the allowance of knees and stomps to the head of downed opponent.
However elbows to the head and soccer kicks were prohibited.
Muay Thai fights were conducted under full muay thai rules with elbows 5 X 3 rounds. 
The Art of War Fighting Championship tournaments are conducted according to the Art of War Unified Rules System, which allows for a variety of striking and submission techniques including soccer kicks, stomps, elbows, and knees to a grounded opponent. 
The following lyrics are taken from the children's music database of the NIEHS:Head, shoulders, knees and toes, knees and toesHead, shoulders, knees and toes, knees and toesand eyes and ears and mouth and nose,Head, shoulders, knees and toes, knees and toes.
An expanded version of the song contains a second verse with the lyrics "Neck, elbows, hips and feet, hips and feet", while another version (with the melody of "London Bridge Is Falling Down") uses "Ankles,elbows, feet, and seat".
The third line may be replaced by "Turn around and jump in the air.
"Other extended versions have the lyrics:Head and shoulders knees and toesKnees and toesHead and shoulders knees and toesKnees and toesAnd eyes and earsAnd mouth and noseHead and shoulders knees and toesKnees and toesFeet and tummies arms and chinsArms and chinsFeet and tummies arms and chinsArms and chinsAnd eyes and earsAnd mouth and shinsFeet and tummies arms and chinsArms and chinsHands and fingers legs and lipsLegs and lipsHands and fingers legs and lipsLegs and lipsAnd eyes and earsAnd mouth and hipsHands and fingers legs and lipsLegs and lipsRepeat the first verseAnother way additional verses are sung is by omitting the first word sung in the previous verse, and, instead, touching their head, shoulders, knees or toes, without actually saying the word.
The last verse consists of no actual singing, just touching what would have been sung or put them back in and sing it much faster.