Brihat Samhita
वल्लीनां गगनतलौन्मुखाः प्रवालाः स्नायन्ते यदि जलपांशुभिर्विहङ्गाः । सेवन्ते यदि च सरीसृपास्तृणाग्राण्य् आसन्नो भवति तदा जलस्य पातः । २८-१३ ॥
If the tender leaves of plants and creepers should be found to grow with their heads pointed to the sky, if birds should be found to bathe in watery particles or if serpents should be found to rest on grass blades, there will be immediate rain.
english translation
vallInAM gaganatalaunmukhAH pravAlAH snAyante yadi jalapAMzubhirvihaGgAH । sevante yadi ca sarIsRpAstRNAgrANy Asanno bhavati tadA jalasya pAtaH । 28-13 ॥
hk transliteration by Sanscript