Hadith 31-137

وَبِهذَا الإِسنادِ عَنْ عَلِىِّ بْنِ أَبِي طالِبٍ‏ عَلَيْهِ السَّلامُ قالَ: عَلَيْكُمْ بِالقَرعِ، فَإِنَّهُ يَزِيدُ فِي الدِّماغِ.

According to the same documentation, Ali ibn Abi Talib (a.s.) said, “I advise you to eat gourds since they strengthen mental powers.”