The first modern writing instrument was likely developed in the Renaissance by Leonardo da Vinci. Aside from the design drawings showing an ink reservoir in a pen, the handwriting in his journals show a consistent contrast throughout, rather than the characteristic fading pattern typical of a quill pen. A fountain pen uses a metal nib with an internal reservoir to hold a water-based ink and transfer it to paper. The pen draws ink from the reservoir through a combination of gravity and capillary action. The reservoir can either be filled manually with an eyedropper or with an internal mechanism that creates a vacuum to bring ink through the nib into the reservoir. Ink can also be stored in a removable ink-filled cartridge.