The Ruyi Jingu Bang
the Ruyi Jingu Bang is featured in the 16th century Chinese novel Journey to the West. It is a staff wielded by one of the main characters, Sun Wukong, who protects and supports the protagonist on his journey.
Ao Guang, the Dragon King of the Eastern Sea gifted the staff to Sun Wukong on his wife's advice, to get rid of their intimidating and chaotic guest who came to the palace in search of a fitting weapon:
"That piece of miraculous iron is one of the nails that Yu the Great used to fix the depths of rivers and seas when he brought the waters under control," said the Dragon King. "What use could it be?" "Never mind whether it's useful or not," his wife replied. "Just give it to him and let him do with it as he pleases. At least you'll get him out of the palace." ~ (The Journey to the West, vol.1,Chapter 3, Adapted from the WJF Jenner translation (Beijing, 1955) by Collinson Fair
The staff is made of iron and is capable of self-adjusting its size according to his owner's wishes:
Sun Wukong hitched up his clothes and went to give it a feel. He found that it was an iron pillar about as thick as a measure for a peck of grain and some twenty feet long. Seizing it with both hands he said, "It's too thick and too long. If it were a bit shorter and thinner it would do." As soon as these words were out of his mouth this precious piece of iron became several feet shorter and a few inches thinner. ~(ibid)
the weapon was even capable to shrink to the size of a needle, to be hidden behind one of the ears of Sun Wukong. It could also multiply itself and fight without the Monkey King wielding it.
