Here is the full list of all 19 Ancient Knowledge achievements.
Find all secrets
Find all plates and notes
Find chamber of secrets
Solve the puzzle of the star gallery
Find a way out of the book maze
Swim on all types of boats
Play all musical instruments
Find a weird booth
Find Ancient knowledge
Find The UFO
It's not related to water
Activate 1 wind mandala
Activate 1 explosive mandala
strange code
Revive the tree
Ring all the bells
Solve all text puzzles
Solve the water problem
Break as many jugs as possible