Bible Study: Not Understanding Sarcasm

When I first read this line in Deuteronomy, I was certain it was sarcastic, or at the very least hyperbolic. It was intended for emphasis, surely, and not to be taken seriously.

6:8 - "Tie [the ten commandments] to your hands and wear them on your forehead as reminders."

This was written in a long list of things to do to remember the Ten Commandments, such as telling your children and thinking about them when you're going to bed and getting up in the morning. I figured this was just another way of explaining how important the Ten Commandments are. But they didn't actually tie the Ten Commandments to their heads and foreheads, surely. That would look really silly!

This illustration was actually in my children's Bible.

Have you heard of the pharisees?
I don't know if this is still a practice in Judaism, but I know the pharisees of the Bible did, in fact, put the Ten Commandments on scrolls into little boxes, and tie the boxes to their hands and foreheads.
I don't mean to deride anyone's cultural practices, because, culture, hey, culture is great. In my culture we wear funny things, too.
But, doing this religiously, don't you think you're taking this a bit literally? This seems pretty obviously hyperbolic.

On the other hand, I guess you can't blame them for taking everything God says literally, given his propensity for incinerating people who step out of line in the slightest.
"We're starving and have been wandering in the desert for years!"
*ZAP*
"Why is Moses constantly telling us to do stupid things, like not eat bacon?"
*ZAP*
"Do the sacrificial goat intestines go on the left side of the altar, or the right?"
*ZAP*

Yeah, I guess I can't blame them for their caution.