Sh'mot 16:13-21 So it came about at evening that the quails came up and covered the camp, and in the morning there was a layer of dew around the camp. When the layer of dew evaporated, look, on the surface of the wilderness there was a fine flake-like thing, fine as the frost on the ground. When the sons of Israel saw it, they said to one another, "Man hu?" ("What is it?") For they did not know what it was. And Moses said to them, "It is the bread which the L-RD has given you to eat. This is what the L-RD has commanded, 'Gather of it every man as much as he should eat; you shall take an omer apiece according to the number of persons each of you has in his tent.'" And the sons of Israel did so, and some gathered much and some little. When they measured it with an omer, he who had gathered much had no excess, and he who had gathered little had no lack; every man gathered as much as he should eat. And Moshe said to them, "Let no man leave any of it until morning." But they did not listen to Moshe, and some left part of it until morning, and it bred worms and became foul; and Moshe was angry with them. And they gathered it morning by morning, every man as much as he should eat; but when the sun grew hot, it would melt.
An omer - 2.08 quarts (2 liters)
The Shabbat is a blessing for man. He can rest from his labor. There is also a higher meaning of entering His rest in which we no longer trust in our works to get us to the other world. This rest is also a blessing to those that believe in Yeshua. Will you still continue to trust in what you can do on your own to reach the other world? Or will you trust the L-rd and enjoy His rest. His rest will bring peace to you with HaShem.
I have come across a belief that actually tries to say that Man (Manna) was not bread but was mushrooms that had a hallucinogenic effect. Don't try to change His word to suit your own agenda to use drugs even if they are naturally made. Adding to the word of G-d will only bring a curse. I can only speculate to what it might have been. I don't think it was anything they had seen before and I would even say that it came down from above.
Manna is symbolic of Yeshua. He is the bread of G-d from above.
John 6:32-40 Yeshua therefore said to them, "Truly, truly, I say to you, it is not Moshe who has given you the bread out of heaven, but it is My Father who gives you the true bread out of heaven. "For the bread of G-d is that which comes down out of heaven, and gives life to the world." They said therefore to Him, "Lord, evermore give us this bread." Yeshua said to them, "I am the bread of life; he who comes to Me shall not hunger, and he who believes in Me shall never thirst. "But I said to you, that you have seen Me, and yet do not believe. "All that the Father gives Me shall come to Me, and the one who comes to Me I will certainly not cast out. "For I have come down from heaven, not to do My own will, but the will of Him who sent Me. "And this is the will of Him who sent Me, that of all that He has given Me I lose nothing, but raise it up on the last day. "For this is the will of My Father, that everyone who beholds the Son and believes in Him, may have eternal life; and I Myself will raise him up on the last day."
Back to the wilderness:
Sh'mot 16:22-30 Now it came about on the sixth day they gathered twice as much bread, two omers for each one. When all the leaders of the congregation came and told Moshe, then he said to them, "This is what the L-RD meant: Tomorrow is a Shabbat observance, a holy Shabbat to the L-RD. Bake what you will bake and boil what you will boil, and all that is left over put aside to be kept until morning." So they put it aside until morning, as Moshe had ordered, and it did not become foul, nor was there any worm in it. And Moshe said, "Eat it today, for today is a Shabbat to the L-RD; today you will not find it in the field. Six days you shall gather it, but on the seventh day, the Shabbat, there will be none." And it came about on the seventh day that some of the people went out to gather, but they found none. Then the L-RD said to Moshe, "How long do you refuse to keep My commandments and My instructions? "See, the L-RD has given you the Shabbat; therefore He gives you bread for two days on the sixth day. Remain every man in his place; let no man go out of his place on the seventh day." So the people rested on the seventh day.
Sh'mot 16:31 And the house of Israel named it Man (manna), and it was like coriander seed, white; and its taste was like wafers with honey.
Honey symbolizes the sweetness of the Messiah Yeshua. He lay in the tomb and did not decompose even though His human nature had died. The worms would not touch His body before He would rise again. He will rule again in the seventh millennium. He is and will be the L-rd of the Shabbat. When we celebrate Pesach, and eat the matzah bread and drink the wine, we remember what Yeshua has done for us. The matzah and wine are only symbolic of His body and His blood.
Matt 26:26-29 And while they were eating, Yeshua took some bread, and after a blessing, He broke it and gave it to the disciples, and said, "Take, eat; this is My body." And when He had taken a cup and given thanks, He gave it to them, saying, "Drink from it, all of you; for this is My blood of the covenant, which is poured out for many for forgiveness of sins. "But I say to you, I will not drink of this fruit of the vine from now on until that day when I drink it new with you in My Father's kingdom."
Back to the omer of manna:
Sh'mot 16:32-35 Then Moshe said, "This is what the L-RD has commanded, 'Let an omerful of it be kept throughout your generations, that they may see the bread that I fed you in the wilderness, when I brought you out of the land of Egypt.'" And Moshe said to Aharon, "Take a jar and put an omerful of manna in it, and place it before the L-RD, to be kept throughout your generations." As the L-RD commanded Moshe, so Aharon placed it before the Testimony, to be kept. 35 And the sons of Israel ate the manna forty years, until they came to an inhabited land; they ate the manna until they came to the border of the land of Canaan. (Now an omer is a tenth of an ephah.) NAS
If we partake of the bread of life and trust in Yeshua we too shall enter His rest.
Hebrews 4:1-13 Therefore, let us fear lest, while a promise remains of entering His rest, any one of you should seem to have come short of it. For indeed we have had good news preached to us, just as they also; but the word they heard did not profit them, because it was not united by faith in those who heard. For we who have believed enter that rest, just as He has said, "As I swore in My wrath, They shall not enter My rest, "although His works were finished from the foundation of the world. For He has thus said somewhere concerning the seventh day, "And G-d rested on the seventh day from all His works"; and again in this passage, "They shall not enter My rest." Since therefore it remains for some to enter it, and those who formerly had good news preached to them failed to enter because of disobedience, He again fixes a certain day, "Today," saying through David after so long a time just as has been said before, "Today if you hear His voice, Do not harden your hearts." For if Y'hoshua had given them rest, He would not have spoken of another day after that. There remains therefore a Shabbat rest for the people of G-d. For the one who has entered His rest has himself also rested from his works, as G-d did from His. Let us therefore be diligent to enter that rest, lest anyone fall through following the same example of disobedience. For the word of G-d is living and active and sharper than any two-edged sword, and piercing as far as the division of soul and spirit, of both joints and marrow, and able to judge the thoughts and intentions of the heart. And there is no creature hidden from His sight, but all things are open and laid bare to the eyes of Him with whom we have to do. NAS