The Coelum philosophorum contains extracts from Arnald of Villanova, Ramon Llull, Albertus Magnus, and John of Rupescissa.
It saw numerous editions, including translations into German (Strasbourg, 1527) and French (Paris, 1546).
Ulstad distanced himself from the philosophical strands of alchemy, and focused on the technical aspects, which he wanted to make accessible to apothecaries, doctors, and other practitioners.
He described the preparation of the quintessence from plants, minerals, metals (gold, among others) and referred to medical applications throughout.
He also authored a short text on the plague (De epidemia tractatus).