CathInfo.com

Oh, come on now, a husband can touch his wife's breasts or buttocks at any time without sin.  There need not be a proximate intention to consummate the marriage act, as a certain amount of intimacy can entail a remote preparation for such activity.

If you are responding to my comments, I reaffirmed that this is not sinful, and was submitting that no priest I can imagine, would ever say this is sinful.  Way, way out on the fringes of the internet, you will find websites that make some pretty outlandish assertions --- that the BVM is God, that there has been no valid pope since Pius IX (yes, Pio Nono, as in Syllabus of Errors Pius IX), that there has been no valid pope since around AD 1100, and so on.  On sites like that, yes, you might find an assertion such as the one you cite.  But other than sites like that, I don't think so.


The closest thing I can imagine would be a couple who is practicing NFP but has a certain difficulty with abstinence and, as a result of engaging in such licit embraces, might be tempted to alleviate their concupiscence through masturbation or non-procreative acts.  But that does not make the intimacies in themselves sinful.  Another close analogy would be when couples are involuntarily separated for a time (e.g., military service, husband has to travel with his job, wife has to go stay with an infirm family member), and reflecting on each other's physical attributes, and intimacies they have shared, could cause them to fall into solitary vice.

Has anyone got any sources or books from traditionalist sources on this topic?

But this same book contains this, which greatly confuses me: 
"Excluding the sodomitical intention it is neither sodomy nor a grave sin if intercourse is begun in a rectal manner with the intention of consummating it naturally or if some sodomitical actionis posited without danger of pollution. - Positive cooperation on the part of the wife in sodomitical commerce is never lawful, hence, she must at least offer internal resistance. However, she may remain externally passive, provided she has endeavored to prevent the sin. She thus applies the principle of double effect and permits the sin to avert the danger of a very grave evil which cannot otherwise be averted; it remains unlawful for her to give her consent to any concomitant pleasure."
Also this: 
"Wives who do not obtain complete satisfaction may procure it by touches imediately before or after coition since the husband may withdraw immediately after ejaculation. Some authors believe she may do so also when the husband withdraws in an onanistic manner. The same cannot be said of the husband should the wife withdraw since the seed would thus be wasted."