First, you need the 5 Lithic Stones. They can be found in the following locations:
1) In the south of Route 42, where there are some bushes and rocks, they form a puzzle in Braille. Press the Z key to open the cave. Inside there will be a Lithic Stone in a vessel.
2) On Route 45, follow the path down until you find a locked box with a password. The code is on the stones in the Lithic Forest (6573).
3) At the end of Route 25, there’s another one inside a mailbox.
4) The one from the Pokémon League you should already have.
5) If you started your game before version 1.0.11, the fifth one is a bit tricky to obtain:
- Go to the bike shop in Cerulean City with 1 million $, and you’ll be given an herb.
- Take the herb to a neighbor in Viridian City, in exchange, she’ll give you the key to an elevator.
- For the elevator, return to Cianwood City and go to Cliff Edge Gate, to the room where there’s a lake and stones. In that room, there’s a hidden button symmetrically placed to one of the missing rocks. Press it and a new room will open. Use the elevator key and read the journal.
- After reading the journal, go to Pallet Town and talk to Professor Oak. He will give you the authorized pass to access Route 13, where the last Lithic Stone is inside a vessel.
I know it’s really complicated. Currently, if you start a new game from version 1.0.11, the Lithic Stone is given to you in Saffron City, but for games that were already started, I couldn’t update it.
Now return to Route 45 (West) and perform the Apacheta ritual with the 5 Lithic Stones. It will take you to an area where you can find the scale and others items.
The start of the new area is a bit difficult (maybe unfair?). I’ll probably end up nerfing it if people complain. I recommend exploring and trying to reach as many cities as you can since they give good rewards.
