Early versions used emeralds, which were later replaced as the primary currency. Players accumulate income through multipliers that are now permanent, meaning you no longer need to keep specific items equipped to benefit from them.
If you are referring to a specific item called a "Piston Trap" block from a niche mod, it likely functions similarly to the mechanism described below. Here is your guide to building a Hidden Pitfall Trap. lovely craft piston trap mod
This is the tricky part. You need the piston to be "ON" (extended) until someone steps on the plate. Early versions used emeralds, which were later replaced