British Library MS. Sloane 3132. Paper. Quarto. 66 folios. 15th Century. 1. Tractatus sic intitulatus, 'Optima ars medicinalis', revera, Johannis de Rupescissa de Quinta Essentia Libri duo. ff.1-38. Begins: 'Dixit Salomon Sapien. cap ViII.' Printed in Duodecimo, Basil 1597. At end there is written: 'Finitus est presens tractatus de Quinta Essentia, anno Dni. MCCCCLXX.