The Book of Bokonon / Bokononism
Bokononism is the native religion on San Lorenzo, and it's easily one of the oddest things in the book. Unlike most religions that claim to have answer to life, the universe, and everything, Bokononism proudly wears its falsity like an ironic t-shirt from Hot Topic.
Bokonon Fanna Fo Fanna
As a symbol, Bokononism basically represents religion as seen in the world of Cat's Cradle. In theory, any religion will do. You just need to pick one and fill in the blank. But, to be fair, the religion seems to draw its inspiration most from the Judeo-Christian Bible. Its scripture, the Book of Bokonon, is written in Calypsos, which read a lot like pop-song-inspired Psalms.
Also, many of these Calypsos take direct inspiration from the Bible. For example, Bokonon writes, "'Pay no attention to Caesar. Caesar doesn't have the slightest idea what's really going on'" (46.16). The phrase is a direct remodeling of Matthew 22:21, which reads: "They say unto him, Caesar's. Then saith he unto them, Render therefore unto Caesar the things which are Caesar's; and unto God the things that are God's" (Source).
A Pack of Foma
The entire religion of Bokonon centers on the concept of foma or harmless lies. And the lies aren't sold as truths, either: Bokonon tells his followers straight-up that he's lying to them. For example, chapter 85 details the beginnings of a mythology for Bokononism, where the sun is named Borasisi and the moon Pabu and the two have a relationship that explains the birth of the stars. Then Bokonon concludes by calling his story, "'Foma! Lies! […] A Pack of foma!" (85.20).
What's Bokonon trying to do here exactly? Bokonon is working under the assumption that a lie is a good thing so long as it helps people live brighter, happier lives. The idea is directly related to Karl Marx's idea that religion is the "opium of the people." In fact, here's Vonnegut discussing that very matter:
Marx said [this] back in 1844, when opium and opium derivatives were the only effective painkillers anyone could take. Marx himself had taken them. He was grateful for the temporary relief they had given him. He was simply noticing, and surely not condemning, the fact that religion could also be comforting to those in economic or social distress. It was a casual truism, not a dictum. (Source)
And Bokononism works the same way in Cat's Cradle. The San Lorenzans are thin, they have missing teeth, and their legs are either bowed or swollen (62.3). Their island produces no wealth of any kind for them. In a word, their lives are miserable. They use Bokononism like any painkiller. It doesn't solve the underlying problem of their existence. It just masks it to make it bearable.
John, after the ice-nine apocalypse, subscribes to Bokononism for the same reason. Of course, he realizes this truism of Marx's comment and Bokononism. That's why he warns us at the novel's beginning that "Anyone unable to understand how a useful religion can be founded on lies will not understand this book either" (4.5).
Boko-maru is a rite in which Bokononists lie on their backs and touch the soles of their feet together. Why? The Bokononists "believe that it is impossible to be sole-to-sole with another person without loving the person, provided the feet of both persons are clean and nicely tended" (72.23).
So, yeah, there you go.
Just as Bokononism stands in for religion as a whole, Boko-maru stands in for religious ceremony. And like Bokononism, boko-maru is completely ridiculous. Even the joke of sole-to-sole sounding exactly like soul-to-soul is meant as one of those "it's so stupid it's funny" type jokes.
Boko-maru may be ridiculous. If you want to make some people angry, you could even argue that all religious ceremonies are ridiculous in their own right.
But that would be missing the point. Boko-maru helps participants feel better about themselves and their lives. So much so that Chapter 92 is solely dedicated to John waxing poetical about how great boko-maru makes him feel. So while it or any other religious ceremony may seem odd at times, boko-maru reminds us that rituals are important for the way they help the participants—and not because the process has any true value.