According to Catholicism, when did people first pray to the Saints?

One of the key differences between Catholicism and Protestantism is the practice of prayer to saints in heaven, which encouraged in Catholicism but absent in Protestantism. My question is, **according to Catholic teaching, when did this practice begin?** I can find many resources from Catholic sources arguing that it ancient Christians prayed to the saints, pushing the beginning back at least to the late 1st or early 2nd century. How much older they believe "at least" means is not clear. For instance, this article at Catholic Answers has a lengthy collection of quotes from the Fathers, the earliest of which cited is Shephard of Hermas. However, it doesn't say when this practice actually began. They give a Biblical argument for its legitimacy, but nowhere claim that any of the Biblical figures *actually did* pray to deceased saints in heaven. So, I can think of several possibilities for the origin that are consistent with that: * It was first practiced by the early church shortly after the Apostles. * It was first practiced by the Apostles after the ascension of Christ, as an inference from his teachings and revelation from the Holy Spirit. * It was explicitly affirmed by Jesus to the Apostles while he was on the earth. * It was already practiced prior to the Incarnation. The last of these is the most interesting. If it's a pre-Incarnation practice, how far back does it go? Might Noah have prayed to Seth, for instance? Or is it an intertestamental development? Or somewhere in between? *Please note I am **not** asking about any of the following:* 1. Critical perspectives on the origin of prayers to saints. (I want a Catholic perspective.) 2. The idea that the saints in heaven pray for people still on Earth. (That's something Protestants generally accept; the point of difference is whether *we* should invoke *them*, not whether they're praying for us.) 3. The theological foundations of the intercession of the saints. (I want to know when it began to *actually be practiced by the Church,* not when it could have been theoretically valid.) 4. Anything related to prayers to angels. (I'm specifically asking about prayer to human beings in heaven.) 5. Prayers on behalf of the deceased, such as 2nd Maccabees 12:42-46. (There's a significant difference between praying *to* and praying *for* the deceased—in the former case the living are communicating directly with the dead while in the latter they are not.)