From the Capitular of Aito, Bishop of Basel, About A.D. 822

Capitulum XXI. Let them know and understand what the crime of incest is, and let each one provide in his own parish that it not happen; and if it has happened, let it be amended as quickly as he has been able. That is, let no one accept for himself from kinship up to the fifth knee (degree, generation). But if it has been done ignorantly, let it not easily be believed, but let it be examined by the judgment of God. And let them not be separated in the fourth knee, but let them persevere in penance all the days of their conjunction. But in the first knee or second, if they have been found, let them know that by perpetrating the crime of fornication they have utterly lost thereafter the rights of matrimony. But in the third, if they have been found polluted by such a crime, let fitting penance follow them, and yet let the rights of matrimony be denied to them, not reciprocally, but with others. But where slaves have been joined who are not of one but of diverse power, unless both lords consent, a copulation of this sort will not be valid.

Namely, those who have been found joined in the fourth degree, this Bishop does not wish to be separated, but to be subjected to continual penance as long as the marriage lasts. Those joined in the third degree he does not separate, but imposes penance, denying them marriages with others after the death of the spouse. But those joined in the second and first degree he separates and takes from them the hope of any other marriage. This Bishop departs from the prescription of the Council of Mainz, Canon LIV, above, and approaches Canon I of the Council of Vermerie. As to the marriages of slaves, he agrees with the second Council of Chalon, Canon XXX, above, and with Basil, Canon XL; cf. in the same place. He also decrees that incest in the first and second degree is an impeding impediment.