A primeira vez que Frodo colocou o Anel no canon foi na casa de Tom Bombadil:
He waited for an opportunity, when the talk was going again, and Tom was telling an absurd story about badgers and their queer ways - the he slipped the Ring on.
Mas a redação em torno disso sugere que ele já estava familiarizado com os efeitos do Anel:
Tom leaned forward and handed it back to him with a smile.
Frodo looked at it closely, and rather suspiciously (like one who has lent a trinket to a juggler). It was the same Ring, or looked the same and weighed the same: for that Ring had always seemed to Frodo to weigh strangely heavy in his hand. But something prompted him to make sure.
[...]
Frodo was delighted (in a way): it was his own ring all right, for Merry was staring blankly at his chair, and obviously could not see him.
Então é bem provável que ele tenha tentado em algum estágio anterior (apesar dos múltiplos avisos de Gandalf de não fazer isso).