Ketubot, Chapter One, Mishnah Five
This mishnah discusses two exceptions to general marriage practice, one a custom in Judah and the second the custom of the priests.
1) He who eats with his father-in-law in Judea without the presence of witnesses cannot raise a claim of non-virginity against his wife because he has been alone with her.
2) It is the same whether [the woman is] an Israelite widow or a priestly widow her kethubah is a maneh.
a) The court of the priests collected for a virgin four hundred zuz, and the sages did not protest.
Section one: The usual custom in Mishnaic times was to wait for up to a year between the betrothal and the wedding. During this time the couple were not supposed to have sexual relations. Generally speaking, the young woman remained in her parental home during this period and the husband-to-be was elsewhere. However, our mishnah refers to a practice in Judea, whereby the groom would eat at his father-in-laws house. This may refer to an extended stay. If he should do so without witnesses that he was apart from his fiancee, he cannot later claim that she was not a virgin at the time of the wedding. Once he has been alone with her, we are suspicious that he has had relations with her, and therefore he loses the right to make a virginity claim against her.
Section two: A widow receives a ketubah of one maneh (100 zuz) whether she was from an Israelite family or from a priestly family. However, the court of priests demanded that virgins from priestly families receive double the normal ketubah payment. We should remember that in this time period priestly families still formed a quasi-elite. Furthermore, occasionally the mishnah refers to court of priests. The priests may have had their own legal system, one which derived from the autonomy they had during Temple times. Priests tended to live in the same area and intermarriage between priestly families was common. While the Sages did not protest against the custom of the double ketubah, one can sense that the fact that the mishnah mentions that they didnt protest, signifies some discomfort with the practice.