القسط الهندي
A root, also called Indian incense, historically ground and either sniffed for throat trouble or placed at the side of the mouth for pleurisy-type chest pain.
عَلَيْكُمْ بِهَذَا الْعُودِ الْهِنْدِيِّ فَإِنَّ فِيهِ سَبْعَةَ أَشْفِيَةٍ، يُسْعَطُ بِهِ مِنَ الْعُذْرَةِ، وَيُلَدُّ بِهِ مِنْ ذَاتِ الْجَنْبِ
“Use this Indian wood [costus], for it holds healing for seven ailments — sniffed for throat inflammation and given at the side of the mouth for pleurisy.” (meaning, not a literal translation)
The hadith names two distinct methods of use tied to two distinct ailments: sniffed (nasal administration) for throat inflammation ('udhrah), and given at the side of the mouth for pleurisy (dhat al-janb) — companions are reported to have followed both administration routes depending on which condition was being treated.
Ibn al-Qayyim lists costus among warming remedies for the chest and respiratory tract, used as a nasal preparation or mixed into oil. He distinguishes between "Indian" costus (bitter, considered more potent medicinally) and a milder "sea" or "white" variety referenced in classical texts, describing the warming, drying quality of the root as suited to cold, phlegmatic ailments of the chest and throat specifically.
Costus root (from Saussurea lappa or related species, depending on which historical variety is referenced) has been examined in some modern pharmacological research for anti-inflammatory and antimicrobial compounds. Noted here as separate modern context, not validation of the classical account.