Disclose Marijuana use on application

I have to have a thorough background check and a lie detector test, the application asks whether or not I have used marijauna- should I say yes? It was when I was about 16 years old and I only did it twice and that was about 20 years ago, and it was like 2 puffs lol I was experimenting. If I say no on the application I am worried I will fail the polygraph test. Is marijuana use something that would prevent me from getting a job if it was that long ago? Unfortunately on the application it doesnt ask when I used it, only IF i have used it.