Instantiating resources through `Resources.Load` in Unity

Foo.cs

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Foo : MonoBehaviour
{
    void Start() {
        // WORKS
        //Instantiate(Resources.Load("BouncyBall", typeof(GameObject)));

        // DOESN'T WORK
        //Instantiate(Resources.Load("..\\Resources\\BouncyBall", typeof(GameObject)));

        // DOESN'T WORK
        //Instantiate(Resources.Load("../Resources/BouncyBall", typeof(GameObject)));

        // WORKS
        //Instantiate(Resources.Load("Test/BouncyBall", typeof(GameObject)));

        // WORKS
        //Instantiate(Resources.Load("Test/Test2/BouncyBall", typeof(GameObject)));

        // WORKS
        //Instantiate(Resources.Load("Test\\BouncyBall", typeof(GameObject)));
    }
}