Step into the hole and activate the piston with a lever. The block will push into your head, and because these blocks are "transparent" to the game engine, you will see through the surrounding stone into caves.
Surprisingly, yes. There is a dedicated community of "legacy players" who still fire up the old 1.5.2 launcher. minecraft 1.5.2 xray
Drag and drop the files from your downloaded X-ray mod into the minecraft.jar . Option 2: The Forge Method Step into the hole and activate the piston with a lever