The jian (pronunciation [tɕjɛ̂n], English approximation: /dʒjɛn/ jyehn, simplified Chinese: 剑; traditional Chinese: 劍; pinyin: jiàn; Cantonese: Gim) is a double-edged straight sword used during the last 2,500 years in China. The first Chinese sources that mention the jian date to the 7th century BCE during the Spring and Autumn period; one of the earliest specimens being the Sword of Goujian. Historical one-handed versions have blades varying from 45 to 80 centimeters (18 to 31 inches) in length. The weight of an average sword of 70-centimetre (28-inch) blade-length would be in a range of approximately 700 to 900 grams (1.5 to 2 pounds). There are also larger two-handed versions used for training by many styles of Chinese martial arts. Professional jian practitioners are referred to as jianke (Chinese: 剑客; pinyin: jiànkè; literally: 'sword guests' or "swordsmen"; a term dating from the Han dynasty). In Chinese folklore, it is known as "The Gentleman of Weapons" and is considered one of the four major weapons, along with the Gun (staff), Qiang (spear), and the Dao (sabre). These swords are also sometimes referred to as taijijian or "t'ai chi swords", reflecting their current use as training weapons for taijiquan practitioners, though there were no historical jian types created specifically for taijiquan.