Bath

Greek scientist and mathematician Archimedes discovered the Archimedian principle when he stepped into his bath and found the displaced water overflowing. This made him excited as he realized the weight of water displaced by an object equals the amount of buoyancy it gets. Thus an object’s volume could be accurately measured by being submerged in water! Unable to contain his excitement, Archimedes leapt out of the bathtub and yelled, “Eureka, Eureka!” as he ran through the streets of Syracuse.

The Archimedian principle has practical uses. It can be used to measure the density of an object, and hence whether or not it is made of gold.

International Bath Day is observed every year on June 14. The day was chosen as Archimedes' discovery occurred precisely one week before the beginning of summer. In ancient Greece, Summer began (and still does today) on June 21st. The week before is June 14th, and this was the date set.

Wikipedia

According to records of payment made to King John of England (1166-1216)'s bath attendant, William Aquarius, the king bathed on average about once every three weeks, which cost a considerable sum of 5d to 6d each, suggesting an elaborate and ceremonial affair. Although this may seem barbaric by modern standards, it was civilized compared to monks who were expected to bathe three times a year, with the right not to bathe at all if they so chose.

Frederick II (1194 – 1250), the Holy Roman Emperor was the first European of this era to take a daily bath.

Isabella I  of Castille (1451-1504) had two baths in her life. One when she was born and one on the eve of her wedding to Ferdinand II of Aragon.

In the 1500s baths consisted of a big tub filled with hot water. The man of the house had the privilege of the nice clean water, Then all the other sons and men, then the women and finally the children. Last of all the babies. By then the water was so dirty you could actually lose someone in it. Hence the saying, "Don't throw the baby out with the bath water!"

Henry VIII created the Great Garden at Whitehall Palace in the mid-1540s. It had a screen installed to ensure that passers by would not see the King of England in his bathtub.

In the 16th century, people believed water opened the pores and allowed dangerous diseases into the body, so they never took baths.

By the late 16th century, the European aristocracy were beginning to use soap for washing the body. However as having a bath was still not a regular occurrence the use of soap for ablutions is still fairly rare, especially for the common folk who couldn't afford it.

Queen Elizabeth I of England (1533–1603) had a bath every three months whether she needed it or not according to a courtier. This was against the advice of her physician.

The French king Louis XIV (1638 – 1715) had his first bath when he was christened, He only took two more baths over the rest of his life, both under protest. 

In the Victorian era, people used rocking bathtubs--literally, tubs of water that could be sloshed back and forth--to recreate the feel of the ocean in their homes. 

There were over 25,000 Chinese working on the American railroads. They bathed and changed their clothes between meals. The Americans at this time only bathed once or twice a year.

700 third class passengers on The Titanic all had to share two bathtubs. One for men and one for women. 

William Howard Taft (1857 – 1930), the obese 27th President of the United States, had a bathtub that could hold four people installed in the White House because he couldn't fit into the present one.

World War II codebreaker Dilly Knox used to solve coded enemy messages in the bathtub. He  persuaded his superiors to have a bathtub installed in his office in the cryptanalysis section of the British Admiralty.

Until the post-war era homes in Japan had no baths - people went to communal baths instead. Below is Sento bathing scene. Japanese woman bathing in a wooden tub (woodcut by Torii Kiyomitsu, late 18th century)[

A crystal bathtub is carved from a single block of the purest white rock crystal, quarried in the Amazon region of Brazil is said to be the most expensive in the world at £530,000.

In Japan, baths, known as of 'ofuro' are deep, short and made of wood. People wash before entering one, as bathing is seen as a leisure activity. 

The inventor of the ATM, John Shepherd-Barron, was lying in the bath when the idea of a cash dispenser occurred to him.

The world’s oldest animal, Jonathan the Seychelles giant tortoise who lives on the island of Saint Helena, was given his first ever bath in 2016.  A loofah and soft brushes were used to protect his shell.

Virginia law forbids bathtubs in the house; tubs must be kept in the yard.

Bubbles from a bubble bath thermally insulate the surface of the water, keeping the bath warm for a longer period of time.

If everyone in the world took a daily bath, our entire supply of fresh water would be get dirty in a single day.