Value of truth-

Shakuntala on being spurned by King Dushyant in his court  reminds him of the pledge he made to her 6 years earlier when they were married in her adopted father's ashram in a forest.He had promised to accept her as his queen and their child as the heir but renegaded on it

She says the following

 The dedication of a tank  is more meritorious than a 100 wells.
A sacrifice is more meritorious than a tank.
A son is more meritorious than asacrifice.
Truth is more meritorious than a100 sons .
A 100 horse sacrifises [ aswamedha yaga] had once been weighed against truth and truth was found to be heavier than such 100 sacrifices .
Truth may be equal to the study of entire Vedas and abulations in holy places .
There is no virtue equal to truth.There is nothing superior to truth.Truth is god himself.Truth is the highest vow.
Then Shakuntala says 'Therefore king violate not thy pledge.'



From Section LXXIV of Adi parva ,book one of Mahabharat