The first altar mentioned in the Word was the one built by Noah after he came out of the ark, after being saved from the great flood. On that altar, he sacrificed clean animals to the Lord.

Mountains represent the Lord because of their height; we need to raise our thoughts above worldly things when "talking" with the Lord. An altar is a small artificial mountain. When it's used in worship, it can call to mind this raising of thought. The fire and smoke that rise from an altar are symbolically being sent to the Lord.

Most altars were made from unhewn stones. Stones represent truths. Unhewn stones - ones that have not been shaped by men - represent truths from the Word, truths that have not been adulterated.

The clean beasts to be sacrificed represent good things, charitable acts done because they are right. The clean birds represent thoughts about doctrine and actions, and about what is right. Presenting these things is an acknowledgment that we have them from the Lord, and a giving thanks to Him for them.

In the Israelitish Tabernacle, the altar of burnt offering represented the acknowledgment of good and the altar of incense that of truth. For this reason this larger altar, which was outside by the door, was made of brass which signifies natural good, while the altar of incense was made of gold, which signifies love to the Lord from whom comes truth.

8410. 'Eating bread to the full!' means that in that situation they enjoyed the good of lower pleasures, as much as they wished to have. This is clear from the meaning of 'eating' as making one's own, dealt with in 3168, 3513 (end), 3596, 4745, and also as enjoyment, 7849; from the meaning of 'bread' as the good of heavenly life, and in the contrary sense the good of natural life separated from heavenly, thus the good of lower pleasures (in the spiritual sense 'bread' means the chief thing that nourishes the soul and maintains its spiritual life, that chief thing being the good of love, as heaven's life demonstrates, which consists wholly of that good. But in the contrary sense 'bread' is used to mean the chief thing that nourishes those in hell and sustains their life, that chief thing being the evil of self-love and love of the world, as hell's life demonstrates, which consists wholly in that evil. To those in hell that evil is good, for to them nothing is more delightful or sweeter; and it is this that is meant here by the good of lower pleasures); and from the meaning of 'to the full' as, as much as they wished to have, since the will is what is filled with good if people are good, or with evil if they are evil.