The “it” is the Baltimore Cathechism, I read it some years ago. I think it was the 60’s version. Maybe they now have out an updated version.
One thing that struck me was it’s pictures. It had all these pictures of an old grey bearded man as God, Jesus as His Son, and a dove. Yet they said they were one. Looked like three to me.
The Cathechism’s “three in one” is just a bunch of double talk - or, should I say triple talk. The Cathechism’s “three in one” amounts to three Gods, plainly and simply. Three separate and distinct Gods.
This, despite the united testimony of the Bible that God is absolutely and uniquely one.
Sigh. So you deny the Holy Trinity?
The images you saw have been considered all but heretical in the Eastern Churches. To visualize the ineffable Father and Holy Spirit is absurd. Here is the proper form of the icon of the Holy Trinity. It is called "The Hospitality of Abraham" since the Fathers believed that the visitation to Sarah and Abraham by three strangers was a "type" of the Trinity.