In the course of study of Massekhet Eiruvin, the Mishna and Gemara have continuously referred to measurements of 2,000 amot out of the city. How were those measurements done? The Mishna (57b-58a) teaches that measurements were taken with ropes of 50 amot, which allowed for accurate measuring over most obstacles. The Gemara on our daf suggests that the passage (Shmot 27:18) describing the length and width of the Mishkan is the source for this idea.
Rabbi Asi said: One may measure only with a rope of afsakima. The Gemara asks: What is afsakima? Rabbi Abba said: It is the nargila plant. This name was also not widely known, and therefore the Gemara asks: What is nargila? Rabbi Ya’akov said: A palm tree that has only one fibrous vine wrapped around it. Some say a different version of the previous discussion, according to which the Gemara asked: What is afsakima? Rabbi Abba said: It is the nargila plant. Rabbi Ya’akov disagreed and said: It is a palm tree with one fibrous vine.
The palm that is referred to is, apparently, the Cocos nucifera, or coconut palm. This tree grows to a height of 30 meters and bears coconuts that can be as large as 20 centimeters in diameter. It is a tree that has been grown since ancient times. In the places where it grows – tropical areas in Asia, as well as islands in the Pacific Ocean – the coconut palm is used for a wide variety of things, including food and drink, cloth, firewood and building.
The ropes under discussion in the Gemara are one of a number of ropes that are produced from fibers of the coconut palm. The best ropes are made from the shell of the coconut that is covered with a fibrous layer, from which ropes are braided. These ropes are considered unique in their ability to retain their strength and size, even when they become wet, as they neither stretch nor shrink.
This quality is obviously essential for taking proper measurements, and it may explain the opinion of Rabbi Yehoshua ben Hananya in the baraita who says that the ideal measuring instrument would have been iron chains, were it not for the passage (Zechariah 2:5) “…and in his hand was a measuring rope,” which he understands to limit biblical measuring to ropes, rather than other instruments.