What is the Pasuk coming to teach us?
Rashi: It is coming to teach us the incredible size of the fruit of Eretz Cana'an. We learn from the rocks that they took from the Yarden. Each man carried a rock weighing 40 Sa'ah, 1 and a person can carry three times as much when others load on him as when he himself picks something up (Sotah 34a). 2
Really, Se'ah is the volume of 144 eggs, between eight and 14 liters. 40 Sa'im of water weighs about half a ton; this amount of rock weighs about 10 times as much
Rosh: Rashi implies that they could carry three times as much, for there were others to load them. If so, eight can carry a weight of 960 Sa'im. (Presumably, Calev and Yehoshua did not help load them. If so, at most two others could load them, and each can lift only 40 Sa'im by himself! Perhaps two Meraglim cut it off the vine when the eight were holding the poles; this is like others loading them. However, after resting it down when sleeping, how could they lift it again?! And what is the source that they found a cluster the full weight of what they can carry? Perhaps if fewer could carry it, others would have carried other fruits. However, perhaps they carried less than their full potential, to enable going quickly. They feared the Cana'anim! - PF)
Seeing as "va'Yisa'uhu va'Mot" implies that two people carried it, why does the Torah add the word "bi'Shenayim"?
Rashi: It teaches that they carried the cluster of grapes on two Motos; eight men carried the cluster. 1
Targum Yonasan: Two men carried it on their shoulders.
Chizkuni, Moshav Zekenim: They made a Mot out of the branch, and carried it on two Motos.
Since both poles were forked at both ends.
How many spies carried the fruit?
Rashi: Assuming that one spy carried a pomegranate, and one man, a fig, 1 it transpires that 10 spies carried the fruit, whereas Yehoshua and Calev declined to carry anything, since the intention of their colleagues was to malign Eretz Yisrael.
Targum Yonasan: Two men carried the grapes, two the pomegranates, and two, the figs. (It seems that the rest carried nothing.)
Which were presumably much larger than those that we have nowadays.
What is the Pasuk now coming to teach us?
Rashi: It is coming to teach us the incredible size of the fruit of Eretz Cana'an. Bearing in mind that each person of that time was able to carry forty Sa'ah, 1 the size of the cluster of grapes that took eight men to carried is mind-boggling.
Rashi (citing Sotah, 34a): as we learn from the stones that they took from the Yarden to place in Gilgal - and a person is able to carry three times as much when helped by others as he is when he lifts something on to his shoulders on his own!
Rashi writes that "va'Yisa'uhu va'Mot" implies two; "bi'Shenayim" teaches that eight carried it. How do we learn this?
Riva: A Stam Mot is two poles (one man bears each pole in front, and one in back). It says about the gold Mizbe'ach "v'Samu Es Badav
Moshav Zekenim: "Al ha'Mot" cannot mean the Badim, for the Mizbe'ach was an Amah wide, so there was an Amah between the Badim. Two people cannot fit between them [for each to hold one of the Badim! Rather, they carried Motos that were under the Badim,]