Letter (paper size) "official" "Government Letter" size, , was used in government, while paper was standard in most other offices. In the U.S., paper density is usually measured in "pounds per ream" (of 500 sheets). Typical Letter paper has a basis weight of paper of – the weight of 500 sheets (a ream) of paper at and at 50% humidity. One ream of 20-pound Letter-sized paper weighs , and a single Letter-sized sheet of 20-pound paper weighs , which is equivalent to 75.19 g/m. Some metric information is typically included on American ream packaging. For example, 20-pound paper is also labeled as 75
Toilet paper human history dates back to the 6th century AD, in early medieval China. In 589 AD the scholar-official Yan Zhitui (531–591) wrote about the use of toilet paper: During the later Tang dynasty (618–907 AD), an Arab traveller to China in the year 851 AD remarked: During the early 14th century, it was recorded that in modern-day Zhejiang province alone there was an annual manufacturing of toilet paper amounting to ten million packages of 1,000 to 10,000 sheets of toilet paper each. During the Ming dynasty (1368–1644 AD), it was recorded in 1393 that an annual supply of 720,000 sheets