When a new candidate is I placed in the northeast corner for the lecture, the reason is explained, but I feel that many times, the reason for the placement is overlooked or forgotten. In most cases this is probably due to the sheer volume of information the new brother is being asked to absorb on that evening.
It was a custom of medieval craftsmen, from whom we Speculative Masons descend, to always place the cornerstone of the building they were erecting in the northeast corner. This custom had come to them from the Jews, who in turn, had taken it from the Egyptians. The latter held the belief that the northeast was the point of the compass from which the sun began its journey when it was first created.
The newly admitted apprentice is placed in the northeast corner because he is held to figuratively represent the cornerstone of the lodge. It is while he is in this corner that he will receive the initial lessons, i.e. light, on which he will build his future moral and Masonic edifice. In other words, the placing of the apprentice in this location is to impress upon him all the qualities required to constitute a well tried, true and trusted cornerstone. Those qualities being truthfulness and uprightness of character, purity and holiness of life.